I've been blogging about SOA stuff...  in actual fact, I'm also actively evangelising on Office Business Applications (OBA). There is an OBA portal. Check these out!

Friendly URL: www.microsoft.com/office/oba/

Direct URL: http://office.microsoft.com/en-us/products/FX102204261033.aspx

OBA video: http://office.microsoft.com/en-us/products/HA102202601033.aspx

Office has evolved so much that it is more than just a productivity tool/suite. Today Office is a platform that can solve your business needs!

If you look at the architecture, the collaboration and workflow piece sits nicely at the productivity tier, a new tier introduced to the traditional 3-tier architecture. In fact, OBA fit nicely to the SOA concepts of Compose (collaboration/workflow) and Consume (office client - Excel/Word/InfoPath/Outlook, etc).

Download this OBA book http://www.microsoft.com/downloads/details.aspx?familyid=736B9708-A332-4AA7-A4D9-5971C486B9E1&displaylang=en to learn about building composite applications using the MS Platform. This book is about composite applications and how they can be developed as OBAs using the 2007 Microsoft Office System.