On Amazon (Kindle) and Smashwords (various formats). Barnes & Noble, Sony, Apple, etc. should follow during the coming weeks, as Smashwords distributes to them. I’ve also submitted a PDF version to Google for their e-book store. That’s my first attempt at getting a book included there. If that one’s okay, I’ll start putting all of my others on Google, as well.
Links for ordering, the cover image, and a bit of info: