The first EPUB venue has now been established: Lulu. As with Amazon/Kindle, it is DRM-free, so you can use it on any e-reader device. Also as before, please pass around this link rather than the Lulu page:

As you might guess from the fact that it has an ISBN, processing into iBooks and Nook is also in progress. So it will soon be available from those stores as well, if they find nothing to reject.

I also realize that at this point, we’re edging closer to software than a fixed piece of art; so I am trying my best to make it work with all e-readers, but I apologize if anything comes out weird for your reader.