I've recently taken the plunge into self-publishing some of my work as eBooks. I went through Smashwords, as well as amazon, since the two aren't linked up. Although Amazon is a definite heavyweight, I dislike that you cannot put free books on amazon.
The Smashwords meatgrinder seemed to work well for me, although I think that Amazon converted my work into a slightly better looking product. I'm only a few days into this, so I'll re-post in a week or two with how it's going!