+1 on the Stax (and Atlantic) stuff. A lot of those lines are easier to play than Jamerson's lines, but they are classics just the same. Have a listen to Eddie Floyd's "Knock On Wood", Otis Redding's "(Sittin' On) The Dock Of The Bay", Wilson Pickett's "In The Midnight Hour", King Curtis' "Memphis Soul Stew" and Sam & Dave's "Soul Man" (all easy-to-find classics). I also think that anyone interested in R&B bass has to listen to Donny Hathaway's "Live" album featuring the great Willie Weeks (there are two live albums by D.H. - check out the one with "The Ghetto" and "Everything Is Everything" on it). Then, of course, there is J.B....