The old-school underground was a mixed bag. A lot of it hasn't aged well (the Fabulous Furry Freak Bros., for example). There's a new book out called
Rebel Visions that's a history of the movement, with lots and lots of strips reprinted. I have an inexpensive book that reprints a few hundred pages of the classic undergrounds, too. I'll look up the title at home and pass it on. It was under $20 for 300-400 pages, and would give you a good taste of what was being done back in the day. In any case, Crumb is the most famous of those guys for a reason. He was a genius!
I like Kim Deitch a lot - he's one of the old timers, and his newer work (Blvd. of Broken Dreams, Alias the Cat) is hallucinatory and fun. I think Seth's comics (It's a Good Life if You Don't Weaken) and Chester Brown's (The Playboy, I Never Liked You) are similar in a lot of ways to Pekar's and Crumb's stuff.
There's a new collection of Aline Kominsky-Crumb's work. Her illustration style is REALLY jarring, and I'd never before read much of her stuff because I was turned off by it. But I read the new book, and it's actually wonderful.
