There are some excellent suggestions here, but I the term Blues encompasses a lot of various styles defined mostly by era. If you are a newcomer to blues you might want to start with the Chicago Blues of the 50's and 60's. This tends to be electric, (Muddy Waters invented electricity) with a full band. I would recommend any of the Chess 50th Anniversary Cd's, probably starting with both Muddy Waters, Little Walter and Sonny Boy Williamson.

A better idea might be to tune into CIUT on Monday's at 6:00 and listen to Let the Good Times Roll, a very good blues show that plays all styles of Blues. It is available online (can someone blueclickything it?)and is followed by Rick Fielding's Acoustic Workshop where it's not unusual to hear a lot of the acoustic Blues greats listed by other posters. (Rick introduced me to Rev. Gary Davis's music) This way you can write down names of some of the artists that you like and can start your blues collection.

Steve