There is a list of 75 "essential" recordings on the Harry's Blues Lyrics page (link in Max's links at the top of the page) It includes the followng compliations (was in chart form so I don't know how th formatting will come out)
RtS
Various artists Alligator Records-25th Anniversary Collection Alligator 110/111 contemporary 2 40 Various artists Blues Masters, Vol. 2: Post-War Chicago Blues Rhino R2-71122 Chicago 1 41 Various artists Blues Masters, Vol. 3: Texas Blues Rhino R2-71123 Texas 1 42 Various artists Blues Masters, Vol. 11: Classic Blues Women Rhino R2-71134 classic female 1 43 Various artists Chess Blues MCA 9340 Chicago 4 441 Various artists Mean Old World: The Blues from 1940 to 19941 Smithsonian Collection 110 various styles 4 451 Various artists The Blues: Smithsonian Collection of Classic Blues Singers1 Smithsonian Collection 101 various styles 4 46 Various artists Trouble in Mind: Original Blues Standards Indigo 2079 various style