Apple's new take on desktop applets. Here are a few I find marginally useful, although I haven't used any of them more than once:

Interestingly enough, widgets appear to be downloadable from the Net without any security warnings, which is pretty dumb considering the things can access pretty much everything on your system. I expect Apple to fix this really soon. Update: It sort of got fixed, and next up on the fix list is uninstalling them, but not having them permanently visible. Bad implementation, I say...