krellin's correct, Ken Burns has a lot of good ones (if you like baseball--I think I recall you're a fellow Mets sufferer, er, fan?--his 10-part "Baseball" documentary is GREAT)...
There are a lot of documentaries on famous authors I like on YouTube...
One on Oscar Wilde...
One on George Eliot...
One on the Bronte Sisters...
One on Charles Dickens' real-world locations (2-parts, with Sir Derek Jacobi...)
Probably my favorite one is one with T.S. Eliot, partially because...well, it's T.S. Eliot, and he's my favorite all-around poet (Shakespeare has sonnets and Milton epic poetry, Eliot's sort of a poet's poet, he could do shorter poems, longer ones, have them rhyme with meter, be free verse, he could plug anything in there from classical literature and symbolism and languages to modern references, he just could do it all) and partially just because of how much and how many different aspects of his life and times they look at, even the stuff that isn't too complimentary too him, like Litvinoff's accusation he was an Anti-Semite and the story behind his infamous poem "To T.S. Eliot" where he blasts him, and he read it in a big public poetry meeting with Eliot present (and the story goes Eliot just leaned over to a friend and said "It's a good poem," and that's it...personally I don't think he was an Anti-Semite, he had Jewish friends, he was just a product of his times and was so used to using symbols in his poetry in classical senses...well, "classically," Jews weren't positive symbols in a lot of Western literature, it's there with Marlowe and Shakespeare and Dickens and plenty other English writers, and then of course he was friends with Ezra Pound...so yeah, I don't see him as an Anti-Semite and just a malicious Jew-hater the way Wagner, say, was, he just was a bit blinded or uncaring perhaps to how those negative symbols really stung with people in a post-WWI and then post-Holocaust world...but then, they WERE classic archetypes, and that's what a lot of his poetry is, twisting around old archetypes and showing them to be "a heap of broken images," so...yeah, I've gone on way too long, watch the documentary!)
:)
Also--
Richard Dawkins has some good ones (obviously)...
And "Planet Earth" is AMAZINGLY BEAUTIFUL, I mean, that just brings out the full beauty of the planet, spectacular, I don't know if it won any awards, I'm sure it won something, and rightfully so, it's breathtaking, check it out!