Some others to look for:
Lil Johnson (Never Let Your Left Hand Know), Memphis Minnie, Henry Thomas (Fishin' Blues), Blind Willie Johnson (Wow), King Solomon Hill, Tommy Johnson (Canned Heat0, Skip James (Hard Time Killin' Floor Blues), Big Boy Crudup, Robert Pete Williams, Sonny Boy Williamson, Peetie Wheatstraw, Roosevelt Sykes, Speckled Red, Hi Henry Brown, Yank Rachel, Frank Stokes, Furry Lewis,....

Aren't you glad you asked? I guess the point is, pick up a good sampler, give it a listen. Ignore the noise of that "old scratchy sound" and some really amazing music will come through.

dw