Default Android 2.1 for tattoo ??

Now that we have custom roms and root access, I think it is time we moved towards android 2.1.

I have fairly decent knowledge of linux kernel and its internals, but zilch knowledge about android and its build systems.

So, any volunteers to give me some links to the android build system, so that I can get started towards that path ?

Does anyone know of some forums where work has started in that direction ?

Shyam