I too reccomend Taj Mahal, great bluesman/folky. I dont think Buddy Guy's been referenced here yet, he's got some great licks.
If you're not too hung up on the white boy part, try some Hot Tuna/Jorma Kaukonan solo stuff, and google David Jacobs Strain. I saw both of these people at the Philly Folk Fest last summer, they completely blew me away. I am also just getting into the Black Key's, a guitar/drum duo that does garage band/blues, they're pretty good.
As far as Jazz goes, basically everything's been mentioned, but I recently listened to Maynard Ferguson's Chameleon album, that's some fine music.