InDesignsecrets.com is your one-stop shop for all things InDesign.
Regular expressionInDesign GREP Help by Jongware
EPUBsecrets — created by David Blatner and Anne-Marie Concepcion, and hosted by Matthew Diener, ePUBsecrets.com is the world’s best resource for all things EPUB.
EpubCheck — a tool to validate IDPF EPUB files
EPUB Straight to the Point book by Liz Castro
Pigs, Gourds, and Wikis — a blog by Liz Castro
Here are some links that might be useful for you to get you started with fixed-layout ePubs:
How to Create Fixed-Layout iBooks by R. Scot Johns
Field Guide to Fixed Layout for E-Books a free ebook on the ins and outs of Fixed Layout EPUB
ePubCrawler -- InDesign to Fixed Layout EPUB converter. (a tool for converting InDesign documents to fixed-layout ePub. It worked very well for me: I had to make only small adjustments to CSS styles).
"On the Goodness of Unicode" by Tim Bray