Hmm, another item:
Threepress Consulting (of Bookworm fame) has a set of
epub-tools available on Google Code, the two main tools are docbook2epub and tei2epub. One quick blurb mentions: " These tools have been used by individuals in ePub-generating projects and have been incorporated into the Calibre ebook conversion suite", although a quick search on Calibre didn't turn up any mention of TEI or DocBook ...