Re: Where's a good place to start for someone looking for good blues music?
Howlin' Wolf - My absolute favorite, the man sounds like an elemental force.
Muddy Waters - The king of blues, arguably, and certainly a fine place to start.
John Lee Hooker - Less booming a voice than Wolf and Hooker but an amazing player.
start with this holy trinity and go from there --
Any of the Martin Scorsese "The Blues" discs from a few years back are good compliations. I also have a nice "Rough Guide to Blues" disc or a "Blues Gold" budget set that are all decent stuff.
Many blues fans divide blues into "Mississippi" blues and "Chicago" blues. It's a matter of opinion but Chicago blues tend to be more poppy and polished, i.e. Buddy Guy or Eric Clapton (I know he's not from Chicago obviously), whereas the Mississippi stuff is rawer, older and rougher sounding -- I prefer it myself but really it's all good.
The "Black Snake Moan" soundtrack is definitely Mississippi blues all the way through. There's an excellent label in Mississippi called Fat Possum that does a lot of more modern kind of garage-blues acts that sound in this vein, RL Burnside, Junior Kimbrough etc. Check out any of their stuff too.
Oh and the Nirvana song is by Leadbelly, he's kind of country blues but any compilation by him is good too.