The OASIS SOA Reference Model group has released its committee draft this is a fantastic achievement and the document is one of the best out there in describing what SOA is all about. Originally it was focused purely on the software side but the committee draft broadens this scope to enable the inclusion of non-software services, for instance those being developed in the OASIS SOA Blueprints group. The reference model has been developed primarily by people who actually do SOA on a day-to-day basis rather than by product vendors, hence its focus on the principles rather than a morbid fascination on Web Services technology.
This SOA reference model works therefore from a long term perspective with a good clarity on principles. Its fairly interesting to look at the membership list this is a specification created by people who deliver SOA.
(updated to include the right link for the PDF!)