Several folks from the extended OBA team and MVPs have been diligently working on an OBA book and I'm pleased to let you know it has now been published! Written by Rob Barker, Joanna Bichsel, Adam Buenz, Steve Fox, John Holliday, Bhushan Nene, and Karthik Ravindran, it's a practical guide to using the Office system as a development platform.
Check it out at: 6 Microsoft Office Business Applications for Office SharePoint Server 2007
Available online via www.amazon.com and other online bookstores.
Incidentally, many of the authors are presenting at the upcoming ODC 2008 so a great opportunity to meet them in person, network with fellow techies, and do a deep dive on the technical aspects covered in the book.