Robert Crumb is one of the most important artists of the 20th Century, without question. He literally changed the landscape of comics, easily as much as Kirby or Steranko (who was Kirby's protege) or Neal Adams, even (who appears to have gone insane.)
Spain Rodriguez just died this year. TRASHMAN is ESSENTIAL reading for anyone interested in comics.
Women? I always loved Mary Fleener but she was more '90's. Shary Flenikken (sic) did TROTS AND BONNIE in Nat Lamp - awesome stuff and WAAAY darker than you'd be able to get away with today.
(As an aside, I'd probably get at least questioned if anyone ever saw Hex's Vatican Vault Full Of Goodies.)
And yes, the Fabulous Furry Freak Bros. Gilbert Shelton.
Harvey Pekar. Blogged about thirty years of his life through his American Spendor comics. Harvey passed away in June of 2010, and the inscription on his tombstone reads "Life is about women, gigs, an' bein' creative."
Russell: saga of a Peaceful Man by Pete Loveday. Very much in the spirit of the Freak Brothers, but utterly British. A great exploration of the new age-festival scene, particularly in the 90s http://www.ukrockfestivals.com/lost-festival.html