I took a look at NaturalDocs today for documenting C# code.  It works by looking at normal comments (/* */ or //) above your methods. It then parses those comments & pretties them up.

All I can say is -- meh. It's very fast, but doesn't parse XML (triple-slash) comments, and it seemed to miss a number of my classes (I think partial classes messes it up).

I don't mean to slight it, because I think it's helpful and fast. I just think it's probably better for documenting stuff like Javascript, Actionscript, etc. If they added support for triple-slash comments & partial classes then it might be more useful for C# etc in terms of its sheer speed.