I've not seen the movie, and don't know Son House's music. But if you want "raw, old blues," you should listen to some tunes by Muddy Waters or John Lee Hooker, two of the great post-war blues guitarists. (I tend to like guitar-driven blues, rather than the more vocal-driven style of B.B. King and other performers known mainly as singers.) Others of my favorite old blusemen are J.B. Lenoir and Little Walter. The latter was especially impressive on the harmonica, one of my favorite instruments.
Even more than of traditional blues, I'm fan of British R&B of the early and mid-sixties. My favorite bands of this era are John Mayall and the Bluesbreakers and Fleetwood Mac of the Peter Green era. Led Zeppelin and Hendrix made this style of music into modern rock and roll by the end of the decade, but it seems like somewhere along the line the "roll," the swinging bluesy feel, got lost and we were left with just "rock."
Except for geriatric bluesmen reliving their glory days, there hasn't really been too much blues or blues-inflected rock in the past couple decades. There are a couple big exceptions, of course -- if you don't know Stevie Ray Vaughn, you should check out his music. All great stuff.
Of bands recording today, I really like
the Black Keys, a duo out of Ohio who play really gritty blues-rock that's a lot of fun. All of their albums are good, but I suggest
Rubber Factory (2004) or their debut,
The Big Come Up (2002).
Eric