For Emacs, check out RLX, a Rogue-like game written in Emacs Lisp. Super wacky! I’ve only looked at the screenies though, not actually tried it…
At FOSDEM I kept telling people I was going to write Space Invaders in Emacs Lisp, using the image support, and perhaps having the invaders be actual (fontified) space characters. Well, dammit, someone else got there first — in 1989, no less.
If you want to improve your Emacs experience and have some time to burn, the Emacs Wiki is great; there’s all kinds of useful info, elisp code, etc, in there.
Chris Blizzard (who I owe some email) pointed out jitblit to me. That’s pretty cool and it reminds me of what Apple is doing with LLVM and OpenGL. We’ll see more of this sort of specialized use of JITs now that they are becoming more common, generic, and library-ized.
I spent a little time looking at Elsa, a parser for C and C++. It seems nicely documented — much better than GCC. But, unfortunately, it doesn’t look like a solid way to start my incremental compilation project. For one thing the parser, according to the documentation is missing most error checks, and mostly assumes your code is valid. This is fine for analysis but not for production.