Ralph Amissah converted a couple of my books to his really exciting format SiSu. SiSu uses simple human-reabable markup and auto-creates several ebook formats, including PDFs, HTML, Docx, Epub, and plain old .txt (my fave!). I've really been looking for an easy way to "single-source" my books from manuscript to finished files, and this looks like a good candidate. Check out the conversions:
The SiSu converter is free/open and runs well on my Ubuntu Linux machine.