really no jam bands? heres a few for you then
Beatles, Stones, The Band, Black Crowes, Stevie Ray Vaughn, Hendrix, anything with Clapton (Blind Faith, Cream, Derek and the Dominoes), Joe Satriani, Allman Brothers, Medeski Martin and Wood, Little Feat (last few border on jam band, but are well worth the recommendation IMO)
If you are trying to broaden you're horizons, try out some reggae. I particularly enjoy it in the summer. Bob Marley (get past the greatest hits, he has a lot of albums), Jimmy Cliff (esp. The Harder They Come disc), Peter Tosh
You should also take a look at the recent jazz/blues thread if you're into that, some real good suggestions there.