I've self-published several books.<p>I primarily use lightning source for print books (both for getting copies for myself and delivering to conferences and for distribution to retail and amazon). I used Lulu for my first book and was disappointed by their responsiveness in case of problems (note this was in 2007/8, so things probably changed since). I've published two books through lightning source and those got into Amazon very quickly, and have been selling quite nicely.<p>For e-books, I use a mix of things. The Kindle store is #1 in terms of revenue for me, and I guess not having a book there is akin to creating an IOS app and not publishing it on the AppStore. Having a book there is a must for discoverability.
I still use Lulu.com to get things on the apple iBooks store and other lesser ebook stores, and to sell the PDFs online. The amount of money I earn from those places isn't enough to justify bothering with each individual submission. For the Kindle store, the submission process is pretty straightforward and there is no need to pay Lulu commission.<p>My two latest books are in progress on leanpub. I think this is a pretty good early-access channel. They now have github support and will generate PDF, MOBI and ePub, so this fits nicely with my workflow and toolchain. Leanpub didn't do anything special in terms of discoverability or promotion for my books, but they were a good channel to republish stuff frequently and let people buy early versions. I plan to re-do the PDF completely for print publishing, but I'll use the MOBI and ePub they generated to sell the books directly on the Apple iBooks and Amazon Kindle stores. I think that's going to be better than just keeping it on Leanpub, again because of discoverability. So if the book is already done, I don't think you'll get much from them.<p>Smashwords.com is another option that looks popular with fiction writers, but I never really did anything there so I can't provide much more than a pointer.