A lot of people have asked and written about how to map Caps Lock to Esc or Control, but I'd like to use the Caps Lock key as a toggle between insert mode and normal mode, and I haven't found anything that addresses how to do this.
(I'd then like to make ShiftCaps Lock do what a Caps Lock alone normally does, for those rare times when you need Caps Lock, like when typing long CONSTANT names. But that's really a separate question that I'll get to later if there's actually a way of accomplishing the first part. All of this may very well be impossible.)
I'm primarily using Windows at work these days, so that's what I care about most at the moment. (Since this is likely to involve hacks of some sort that are Windows-only, I'll ask a separate question for OS X, which I also use.)