Several different software programs either support or plan on supporting the ePub format. The ePub format is an open standard for ebooks by the International Digital Publishing Forum. Since it’s an open standard, anyone can make a program to read or create ePub books, and anyone can make an ePub ebook.
I’ve reviewed several different programs that both read and create ePub books. If anyone is wondering where I hear about these programs, I primarily use two sources: Google, and Teleread. Also, lately I’ve gotten a few e-mails asking me to review a program, so I’ve reviewed those as well. Also, Wikipedia has a list of ePub readers for different platforms on it’s ePub Page.