I'm a big fan of the "Friday links" posts presented by Mike at Blue Onion Software, and have held off doing this myself because he does such a great job. But I realized that posts like this are more useful for me to refer back to, since there are many times I come across an awesome new project that I have no use for... yet. So, at the risk of being a copycat, here goes...
jqMetro
I'm tired of the coda slider look, and I think this interface is far more intuitive.
Amplify.js
For a relatively small app, this looks great. I can think of a few uses already.
Apprise
Yet another jQuery plugin, that finally gives us some easy, pretty alerts and basic dialog boxes.
A short list to start with - can you tell I like jQuery?