anything by Buddy Guy, John Lee Hooker, BB King, Eric Clapton's Sessions for Robert J (basically covers of robert johnsons music), Muddy Waters.
BB King's cd 80 is really good basically covers of old BB King songs with other artists. I suggest "early in the morning" w/ van morrison , "Tired of your Jive" w/ Billy F. Gibbons, "Hummingbird" w/ John Mayer, "All Over Again" w/ Mark Knopfler (this song sometimes gets my eyes watering. just the playing in it...whew)
buddy guy and junior well's live cds are really good too.
look for a song called "Red House" its covered by G3 its a good version, and numerous other covers of it are good too.
another really good guitar song "Trouble in mind" done by Jerry Lee Lewis featuring Eric Clapton is really good
and here's some more buddy guy stuff thats a little more rock then blues, but some really awesome guitar playing: