Developing Quality Technical Information : A Handbook for Writers and Editors

IBM Press Series--Information Management (not DITA but recommended as a good book on "topic based authoring") (Available from Amazon.com.)
XML.org Focus Areas: BPEL | DITA | ebXML | IDtrust | OpenDocument | SAML | UBL | UDDI
OASIS sites: OASIS | Cover Pages | XML.org | AMQP | CGM Open | eGov | Emergency | IDtrust | LegalXML | Open CSA | OSLC | WS-I