Clued in from this article. I found MochiKit, it’s a JS library.
I haven’t used it extensively, just looked over the examples really, but it seems cool. I was particularly interested in the signal code. This is something I had meant to write myself for a while now, but I never got around to it. I plan to mess around a bit with it here over the long weekend and see what buggery I can get up to with it. Also, Eric seems to like YUI!, so I want to look into it some more as well. I have messed with it in the past, and I *almost* used it’s calendar widget for an app at work, but I ended up going with datepicker, from http://nsftools.com. I don’t remember why.