I should have been more clear - I'm not looking for an IDE (or OS, emacs I'm looking in your direction), I'm looking for a small, lightweight text editor that happens to have good hooks support so I can extend it in particular ways.

Eclipse is a full-blown IDE, and way overkill for what I need. I might as well be using Word to write emails, y'know? (I've seen people do that, and it drives me nuts.)