Feature Stapling

http://blogs.msdn.com/cjohnson/archive/2006/11/01/feature-stapling-in-wss-v3.aspx
http://sharepointmagazine.net/technical/development/introduction-to-sharepoint-feature-stapling-part-1
http://www.sharepointnutsandbolts.com/2007/05/feature-stapling.html
http://www.sharepointblogs.com/jasonmedero/archive/2007/07/24/site-definition-customizations-versus-using-feature-stapling-part-1.aspx