I personally have used Lulu and Smashwords. I didn't like working with Lulu because they have such high base prices that books such as my short 68 page cookbook ended up having to sell for $20.99, and out of that I think I make $1. :( Not cool!! However, the end product is fairly high quality, except for the cover if you are like me and can't make cover art. I LOVE using Smashwords because it is FREE and if you follow the style guidelines they submit your eBook to major retailers for FREE as well!! Plus, it has some higher commissions - I get about 65% of the purchase price of my eBook back, rather than the measly amount through Lulu.
Anyway, if you'd like to read about all 7 options, just click here for the article.