Some top-notch Blues albums beyond the mainstream:

R.L. Burnside - Too Bad Jim
John Campbell - One Believer
Jimmy Dawkings - Hot Wire 81
T-Model Ford - Bad Man
Buddy Guy - Sweet Tea
Omar & The Howlers - Muddy Springs Road
Jr. Kimbrough - All Night Long
Guitar Shorty - Watch Your Back
Seasick Steve - Dog House Music
James Blood Ulmer - Birthright