"What is Hedgehog"
The Hedgehog is a defensive opening for Austria. It was devised by Richard Sharp in 1975. The rationale is easy enough: You are uncertain whether or not Italy and Russia are allied with you or with each other against you, and you're acutely aware that their standard anti-Austrian openings put you in a serious bind, with armies in Venice, Tyrolia, and Galicia just in time for Autumn 1901. Your goal is to neutralize this as much as possible.
The original Hedgehog moves are:
Army Vienna -> Galicia
Army Budapest -> Rumania
Fleet Trieste -> Venice
The goal was to bounce Russia in Galicia and throw a serious wrench in Italy's plans. If Italy runs the more popular anti-Austrian opening -- the Obriani Attack, which sends armies to Tyrolia and Venice -- then the fleet in Trieste stands off the army Rome in Venice, isolating the Italian armies in Rome and Tyrolia. Tyrolia can at best take a wild chance shot at Vienna or Trieste, and Rome is useless. And if Italy tried the Austrian Attack (armies to Trieste and Venice), he's done. Everything stands except the fleet in Tunisia. And in all cases the Russian's only really serious move against Austria -- to Galicia -- got bounced, and if he decided not to play A Mos -> Ukr, he's dependent on Turkey and Germany to build at all, thanks to A Bud -> Rum.
However, the original Hedgehog was soon abandoned due to the fact that it was overly anti-Russian. First, if Russia did play A Mos -> Ukr and bounce Galicia, now *Austria* is dependent on Turkey to build at all, because Russia can force Rumania and Turkey can move Bulgaria to Serbia and deny Austria any of the Balkan centers. Second, if Russia was not hostile in the first place, Austria has basically ruined any serious prospects for alliance. Turkey is guaranteed to get Greece in A01 unless Italy is a masochist, and that sets Turkey up to get Serbia in S02. Ironically, the standard Hedgehog's aim -- defending from an RI attack -- sets the stage for a beast just as dangerous to Austria: the Juggernaut.
Enter the Southern Hedgehog. This setup decides not to pick a fight over Rumania in exchange for a guaranteed build and the all-important influence over Greece. The moves:
Army Vienna -> Galicia
Army Budapest -> Serbia
Fleet Trieste -> Venice
The same rigorous defense is played against Russia and Italy, but by moving to Serbia, Austria doesn't anger Russia as much, and can move to Bulgaria to cut off Turkey's armies just like the fleet in Trieste bisected the Italian military: by isolating the army in Greece, Austria severely hinders Turkey's mobilization in the Balkans.
The moves to Galicia and Venice are often announced beforehand. Austria generally WANTS to standoff in Galicia, so the army remains in Vienna and is able to provide defense if Italy attacked. And Venice is just a dead-end if the fleet gets there, not to mention an Italian center, so the fleet needs to remain in Trieste. Russia won't be offended by the move to Galicia, as the province is so often the site of a standoff that it's practically standard-issue to see it anyway. Italy *generally* isn't offended by the suggestion of a move to Venice, either. Not unless Italy's attacking Austria, anyway! An all-out attack against France probably warrants the standoff: it keeps the army in Rome so that Italy can convoy it to Tunisia via Tyrrhenian Sea, and it does prevent Italy from running the Alpine Chicken (where the armies move Rom -> Ven -> Pie, then Pie -> Tyl and Ven -> Tri in A01). And against Turkey you're seeing a Lepanto: this time, Italy should move Rom -> Ven -> Apu, standing off in Venice so Austria can safely move to Albania while Italy continues the convoy to Tunisia from Apulia. And if Italy is moving against Austria, well... damn good thing you used the Hedgehog!
The weakness of the Hedgehog, though, is its surrender of the Balkans, at least temporarily. It should not be played unless Austria has a strong suspicion that Italy is after him. If Austria isn't certain of it then there's no reason to surrender the second build from Greece. Austria can still recover momentum in the Balkans if Italy didn't attack, which makes the Southern Hedgehog the best opening for gunboat. Italy rarely attacks Austria in gunboat, and if Serbia moves to Bulgaria in A01 with Trieste moving to Albania, Austria can take Greece in S02 and possibly Bulgaria in A02, suffocating the Turkish offensive with two units while using the remaining units to stave off and eventually defeat Russia. And again, if Italy did move on Austria, good thing you played the Hedgehog!
But in a full press game it's an opening that should be used in extenuating circumstances. Italy should be subverted through diplomacy if at all possible.
", precious?"
Taken. ;)
"also Eden, could you explain Northern Yorkshire"
That's simply the English Northern Opening (fleets to NWS/NTH) with the army to Yorkshire instead of Edinburgh. The defensive advantage compared to Edinburgh is obvious: If Russia and France are hostile (France moves to the Channel, Russia moves A Mos -> Stp), then A Yrk can cover London while England supports itself to Norway. The Northern Yorkshire is the only opening that lets England guarantee itself a build in 1901 against the worst possible opposition.
But it gets better. It also leaves England with the best shot at two builds. A simple look at the geography would indicate that Norway is better captured by a fleet, Belgium with an army, instead of vice versa. Only three openings can do that -- the Wales Southern Opening and the Northern Opening (Yorkshire or Edinburgh). The Wales Southern Opening can leave you buildless easily (not to mention up shit creek if France opens to the Channel), and Yorkshire and Edinburgh are the same here (the convoy goes through North Sea, not Norwegian Sea). Yorkshire has the defensive advantage. So in going for one build Northern Yorkshire is alone the only way, and for two it's the best -- all in all, the best opening.
"Lepanto"
Probably the most easily recognized Diplomacy opening. Italy moves an army to Apulia and the fleet to Ionian Sea, then convoys the army to Ionian Sea, keeping the fleet in Ionian Sea. Italy builds a fleet in Naples, then moves F Nap -> ION and F ION -> EMS. In the fall, the army in Tunisia is convoyed to Syria or, if Italy's feeling lucky, Smyrna. The advantage is that if it works, Italy can really implode the Turkish position, especially with pressure from Russia and/or Austria. The disadvantages, though, are many: it relies on an Austrian not deciding to stab Italy (as only one army is left to defend three home centers!), a Frenchman not stabbing by sending fleets into the Mediterranean, and a Turk not seeing the Lepanto coming (building F Smy with the almost-certain gain of Bulgaria allows Turkey to block the move to EMS). Even then, Italy is not likely to see a fifth center until 1903 and Turkey can easily last until 1905. Getting the patience out of Austria and France necessary to pull this off is hard to do. It also requires commitment from the opening move: the convoy via Ionian Sea is a MUST to execute the Lepanto, which means the army has to be in Naples or Apulia and the fleet has to be in Ionian Sea on the first turn.
Now, there are a couple of important deviations. The first is the stab Austria variant: the Ionian fleet moves to Adriatic Sea instead of Eastern Mediterranean Sea, and the army gets convoyed to Albania instead of Syria (or, again, if feeling lucky, Trieste instead of Smyrna). This is similarly risky because France can still run into the Mediterranean, but Turkey is far less effectively placed to attack you than Austria, so it's safer. The downside is that you still have insufficient forces to really do anything and will need a multilateral invasion to be successful. This should be used when you start with the Lepanto but realize before the S02 committing moves that it's a bad idea to continue.
There's a less used French variation, where you simply move Ven -> Pie, ION -> Tun -> NAf, Nap -> TYS, followed by fleet moves into GoL and WMS. The advantage is that France almost never sees this coming... the disadvantage is that you are still leaving yourself wide open to Austria and this time you're also vulnerable to Turkey (though again Turkey is going to have a little trouble conducting effective reprisals). You're also basically incapable of getting anywhere quickly unless you, again, are part of a multilateral invasion.
Essentially, the Lepanto in its different variations works IF Italy has help from someone else. It's not a way for Italy to go solo and profit.
"Houseboat"
The Houseboat is a weaker Hedgehog. It employs the logic of the Hedgehog without the most critical move: Venice to Trieste. It does stop the Austrian Attack but does nothing against the more popular Obriani. The hold in Trieste is clearly meant to defend from Italy, but there's no reason not to move to Venice from there.
"Galician Balkan Gambit"
This is the ideal Austrian opening. It requires Italy to be pro-Austrian, and is obviously very weak against a hostile Italy (though not *too* weak; read on), but if Italy doesn't attack then Austria has the two builds it needs to take on Russia and Turkey. The move to Galicia is generally intended as a bounce, but if Austria guesses right on trusting Italy it might be advisable to try and take it anyway. Warsaw can be swiped, and Rumania can be stood off or even taken with Serbia support, though that does require Turkey not to try for Greece. And if you REALLY want a nice move, Galicia can move to Ukraine in A01 and give Russia ten different kinds of hell for 1902. It forgoes the third build, but the third build is unlikely anyway and better to be in Ukraine than Galicia.
The disadvantage is clear: If Italy moves to Trieste and Venice, you are in deep shit. Italy is guaranteed a second build, you're not getting more than one and if Russia and/or Turkey smell blood in the water, it could be a quick out. Still, you at least keep Russia from joining in (right away) with the move to Galicia. And, if you standoff Galicia, you're in business even if Italy opens hostilely, should he decide to use the Obriani: Vie S Alb -> Gre covers Trieste and Vienna, and you can still get a build out of Serbia. You might still be in trouble, but at least Italy might be dissuaded from further attacking.
"and while you're at it the Key Lepanto as well - just because I love the Key"
So I noticed. The Key is a Lepanto where Venice moves to Trieste, then to Serbia with support from Austria, while Austria takes Greece and (in some variations) Rumania. Italy typically builds two fleets and uses its army in Serbia as an extension of Austria's forces, while his other units carry out the standard Lepanto invasion. The chief advantage is surprise. The chief disadvantage is that if Italy crosses Austria, Austria is dead. Worse, Italy doesn't even have to do the typical Rom > Ven > Tri stab; he can follow the Key and get Turkey to bounce Serbia, keeping Trieste "without stabbing" Austria. Either double cross is death for Austria. If it works, though, you have everybody stunned, and you can probably take over the East easily with Italian help. It's just incredibly risky, arguably the riskiest alliance play in the game.