Some articles from around the net that talk about SCA/SDO and Tuscany. Candidates for the Resources section of the Overview page on the web site.
Feathercast Issue 35 (http://feathercast.org/) talks about Apache Tuscany
Build mashups with the Service Component Architecture and Apache Tuscany - Andrew Borley
Using the Eclipse SOA Tools Platform plug-in and Apache Tuscany - Tyler Anderson
Service Component Architecture (SCA) lets you invoke components from different technologies - Dan Becker