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?