I have been discussing this in the forums and I think its time to act.  You can find my post here.  I basically start the list of Content API, Membership API, Profile API.  I know a lot of this was started in new genesis and I want to continue that research.  ASP.NET 2.0 is more API based as it has 4000 new apis installed since 1.1.  I would appreciate feedback of any API's you think should belong in rainbow.  An API should be created to do complex processes with simple API calls.  I envision a Rainbow where its core is simplified by a couple API's.   Even if we numbered them in the 50's at least you could know where to go for what process.  Also if these APIs are upgraded/developed on in the future then developers would not need to change their code to use the new framework.  Think of a rainbow with a BizTalk API...