So far this is what I have found out
Amazon kindle (AZW format)
Format your content using HTML then upload to Amazon to convert to an AZW file. Book has to be sold for at least .99c with Amazon always taking 60%
The ePub format is probably going to be the best one to go with as the Sony eReaders and the new Apple iPad use this format.
Here is a list of ways to format ePub files, but for my money I am extremely pleased that you can do it from Indesign CS4.
Most of the ePub websites I have found are based on the 'everything is free' model. As I have blogged previously I would like to see a pay model website for like what lulu.com does for POD publishing.
Comparisons of eBook readers
Any suggestions, thoughts, links, ideas are welcome in the comments