I don't know whether anyone's mentioned it yet, but I recommend the 1968 album "Super Session" by Al Kooper, with Mike Bloomfield and Stephen Stills each playing guitar on half of the cuts. Bloomfield's playing here is still some of the greatest blues guitar ever, not in the SRV macho, Texas style, but in the B.B. King mold-- very melodic, with incredible phrasing and a jazz influence. Very tasty.
The previously mentioned "London Howlin' Wolf Sessions" from 1971 is cool... Wolf was old and sick by then, but the English guys, including Clapton, Winwood, Wyman and Watts, play like genuine bluesmen, and Clapton is particularly fantastic. (It was recorded in 1970 at the height of the Derek and the Dominos period, when he was on fire.)
Leslie West's first album, "Mountain", from 1969 (I think) is interesting. He plays guitar with a great feel, and the music is bluesier than on the subsequent albums when Mountain became the name of the band.
The J. Geils Band's "The Morning After" from 1971 (I think) is blues rock with a bit more gritty rock and roll and R&B mixed in. Rock-solid rhythm section, too.
The Allman Brothers Band's "At Fillmore East", from 1971, is a true classic. On it you'll hear a lot more than blues and rock, but everything is astounding. In my humble opinion, Duane Allman (slide guitar, lead guitar) was the most gifted improviser, on any instrument, during that entire era. A genius. The way the whole band plays like one being is unlike anything else I've heard.
Finally, find something by Canned Heat. They were a late '60s band, sort of rock guys who were hard core blues devotees. They largely played John Lee Hooker style stuff. Larry "The Mole" Taylor is a bass player who should not be missed.