A lot of beginner musicians assume (incorrectly) that the twelve bar blues is the only real blues progression. While it is, by far, the most common, there are additional progressions you can use in your arsenal.
Two easy blues progressions, which are normally based on major or 7-chords with some roots pulled from the minor pentatonic scale, are outlined below:
A lot of new musicians think all blues tunes have to sound like B.B. King after a good long drinking spree, but blues progressions can be found in songs like Life in the Fast Lane by the Eagles, Can't Buy Me Love by the Ruttles...err...the Beatles, and Bono wailing he "still haven't found what I'm looking for" with U2.