I’ve formatted all my ebooks and print books myself using various tips and tricks I found online and OpenOffice. OpenOffice is a free, open source office suite that works on both Windows and Mac. It does everything I need it to do to publish my books in every format. If you haven’t downloaded it already, you should seriously check it out.
For the versions of my ebooks sold directly from my site (via the Tribe portal), I use OpenOffice to create the PDF files by clicking the handy ‘Export Directly as PDF’ button on the toolbar. I use Calibre to generate the mobi (Kindle) and ePub (every other ereader) files. Calibre is also free to use, but donations are welcome. I use it in conjunction with OpenOffice .odt versions of my ebooks, which I format in a style that’s almost identical to standard Kindle formatting.