I've really only been selling my books via comic fests. It's really the best way. But... I need to reach out to you internet folk.
I've gone and done the simplest thing I could figure out and I put a bunch of them up on Etsy. Here's the link:
http://www.etsy.com/shop/swellzombie
I appreciate every sale and I usually throw in some extra little bits. If you mention this blog I'll throw in a copy of INTRUDER with each sale!