The latest release in an ongoing bender of Greasemonkey scripts involving jQuery: the jQuery Selector Tester!
This little guy will hang out on your internet and highlight all the elements that match the selectors you type in. Indispensible for development! It doesn’t remember where you leave it on the page yet so it’s probably easiest to turn on only when needed.
Find some more of my jQuery Greasemonkey scripts here. They are sometimes ahead and sometimes behind what I post on the blog.