Talking of Javascript, I've been playing with this recently. It's great. You write code in C# (against a special library, instead of the BCL), you get all the cool VS2008 IDE stuff like Intellisense and refactoring and type-safety and compile-time checking, but it builds to Javascript. Proper cross-browser DOM support and so on. The debug builds are readable code and the release builds are minified, or whatever it's called.
Doesn't support jQuery yet, but it's supposed to be coming this year for the v1.0 release.
