I’ve just released beta 20080322, which comes with a published API. Docs are at:
sublimetext.com/docs/plugin-basics
sublimetext.com/docs/plugin-examples
sublimetext.com/docs/api-reference
There’s still more functionality that needs to be exposed, and more introductory documentation that needs to be written, but I feel this is a pretty good start.
I haven’t mentioned it in any of the above docs, but within the console you have access to two variables, view and window, which are a good place to start exploring.