http://jfattic.blogspot.com/2008/08/intro-to-sharepoint-soa.html
Can Sharepoint be molded into a SOA? IMHO, Sharepoint's web services already expose many services, and also workflows can be exposed as web services. Also, custom built workflow activities can be treated as mashup-able components (recently my company did build such a mashup/SOA solution for a government agency)