Blues covers a range of music, as reflected in some of the posts made here so far. Joey B. is electric blues reminiscent of Clapton in the formative years (although Joey has gotten too hard rock for me, still love him, and have seen him a bunch of times). John Lee Hooker is old school and lasted a long time. Here are a few recommendations, off the top of my head:
HooDoo Man Blues- Junior Wells and Buddy Guy- if you are a vinyl guy, go for the audiophile 45 rpm pressing. You can smell the cigarette smoke in the room, this album has all of the vibe of a blues bar in the early 60's. (not that I was spending time in them then);
Muddy Waters- find a collection of his earlier stuff from the Chess era. Ditto on Howlin' Wolf and Little Walter. If you like harmonica, Sonny Boy Williamson II (there was a Sonny Boy Williamson I).
Early Stuff, acoustic, delta, country blues: Skip James, Big Bill Broonzy, Son House, Blind Willie Johnson ("Dark was the Night" and "It's Nobody's Fault but Mine"); Bukka White ("Shake 'em on Down"), just to name a few (and there were many who are just as good, I am leaving out the obvious, R Johnson, but you will know Crossroads, at least, which is attributed to him). The early stuff, at least on the early recordings, is not sonically spectacular, but hugely musical.
Female Vocal: Bessie Smith, Billie Holiday, Big Mama Thornton, some Etta James, Janis Joplin.
Almost every electric blues artist from the 60's either 'borrowed' or acknowledged their direct influence by earlier artists, so you can work through Cream, Jimi, early Peter Green Fleetwood Mac, Led Zep, Johnny Winter, and get solid harder edged blues that has antecedents. For example, Junior Kimbrough was a big influence on Black Keys, so if you like them, you'll probably like Junior.
Jimi's Red House on Concert in the West is brilliant.
Try creating a blues channel on Pandora and you'll be exposed to alot.
There is also alot of literature to read and if you are interested, I can recommend some books.
