Right, given that I wrote my dissertation on exactly this subject (it was entitled something along the lines of 'Are we justified in blaming Germany for WWI,' which does mean most of my research looked at what happened in Germany from roughly 1871), I feel fairly well qualified to stick my oar in. So:
@ottovanbis - Sorry, you're wrong there. That simply isn't the case, Bismarck, whilst being fairly pragmatic, was one of the people driving Germany's quest for colonial power (one of the key factors IMO). Plus, as someone mentioned, Bismarck died before 1900, which was about when things really got going.
@Invictus - Two points: 1) "Wilhelm II and his wacky antics set up the situation that made the First World War possible." Yes, I agree with you completely. That man did very little to encourage good relations with any of his neighbours, and, between him and Tirpitz, contrived to seriously piss off the British.
2) Bismarck wrote that constitution when he was effectively Wilhelm I's right-hand man, and pretty much had freedom to do what he wanted. Sadly for Bismarck, Wilhelm I died and left Wilhelm II to screw things up.
There is something else that should not be overlooked here either: Up until the mid-1960s, German historians all shared the belief that it was completely unjustifiable to have blamed Germany for WWI. Since then, however, the majority now agree that it was, indeed, Germany's fault. There are so many things that occurred in Germany that make it clear that everyone involved was on a war footing, they just had to wait for a catalyst to set it off: Germany did not want to appear the aggressor. That catalyst (and if anyone who doesn't know the definition of a catalyst in Chemistry, it is an agent [that comes out of the process unchanged - we can ignore that part] that speeds up the rate of a reaction - i.e. the reaction was going to happen ANYWAY) was the shooting of Franz Ferdinand, and it just gave Germany the excuse to start the war that they already wanted.