Early Fleetwood Mac

The pre-70s stuff is fuckin' badass. I have a bootleg of a show from 1970, and it's all hard rock/blues infused stuff. Awesome music; Rattlesnake Shake is pure badass.

I'd say try the album 'Then Play On.'
 
Definetly awesome stuff. Then Play On is of course essential, particularly for the epic masterpiece Oh Well.

But also consider going for the live ablum Boston Tea Party. Great stuff.