For a solid background in Blues I gotta spend some time with the Three Kings. (That's Freddie, BB, and Albert y'know?).
When I want to 'break out' and refresh my senses with something fresh and original, there's nothing like "Second Winter" from Johnny Winter! He got more mainstream as time, and other troubles wore on him, but that one album stands out for all time.
A band I've never seen mentioned here that I particularly enjoy, is Savoy Brown. Again, their early stuff is the best. Kim Simmonds' guitar work was the key to that band. The rest of the members rotated out frequently, but most of them were phenominal. Bob Hall's piano lines were amazing. "Blue Matter" should be in every serious Bluesman's collection!