I use GNU Emacs as my text editor. It's old and crusty, but I love it. It's missing some features compared to some of the newer IDE type editors that have access to the symbol tables from compilation, and it's ludicrous that we're still using text files for programs, but it serves me well, and the complete programmability is awesome.

Here is my .emacs file. I haven't cleaned it out in a while, so it's got some really crufty old stuff in it. I'm actually trying to move back towards the default key bindings so that I can just use an empty .emacs when I have to, but I do make ctrl-; act like ctrl-x do my left hand doesn't fall apart from RSI. And, of course, you have to remap caps lock and ctrl.

I recently discovered the awesomeness that is Emacs Calc. I use Mathematica for real stuff, but Emacs Calc is very useful while programming. You can see some functions that use its bignum capabilities in elisp at the bottom of my .emacs.

I also use a modified allout outline mode a lot, for todo lists, worklogs, and the like. Very useful. I've written some code to sum up hierarchical time estimates with it as well.

As for the future, it looks like they're finally putting soft returns into Emacs. That was the epitome of what I call the poisonous You Don't Need That mentality.