Here are some references that I have used in the past, and in some cases use on a regular basis. I hope they’ll help you as well in your quest to integrate social networking into your OBA.
Inside Microsoft Office SharePoint Server 2007 by Patrick Tisseghem (Microsoft Press)
6 Microsoft Office Business Applications for Office SharePoint Server 2007 by Rob Barker, Steve Fox, Bhushan Nene, Joanna Bichsel, John Holliday, Adam Buenz, and Karthik Ravindran (Microsoft Press)
Professional SharePoint 2007 Development by John Holliday, John Alexander, Jeff Julian, Eli Robillard, Brendon Schwartz, Matt Ranlett, J. Dan Attis, Adam Buenz, and Tom Rizzo (Wrox)
Office Developer Portal: http://msdn2.microsoft.com/en-us/office/default.aspx
VSTO Developer Portal: http://msdn2.microsoft.com/en-us/office/aa905533.aspx
SharePoint Server 2007 Developer Portal: http://msdn2.microsoft.com/en-us/office/aa905503.aspx
OBA Central: www.obacentral.com
Popfly: www.popfly.com
Information on RSS XML Documents: http://cyber.law.harvard.edu/rss/rss.html
Lawrence Liu’s social networking blog: http://sharepoint.microsoft.com/blogs/lliu/default.aspx