The teleread blog just posted a link to
.epub eBooks tutorial which might help. However, I have been unable to download any example .epub documents from this site or from IDPF (all are page not found). I was able to get examples from Adobe's
digitaleditions library.
I don't know how there can be a true "standard" without at least two readers and at least two sources of e-books. At the moment, all we have is "Digital Editions" complaint documents.