Krugle is an already seriosly good contender to Google Code Search, for digging up the source code of that <whatever> it is you are looking for. I love the interface which lets you slash down to the particulars you want, if you want to, or not. With a slap-on license filter, it would beat Code Search hands down. (They seem to consider adding it already, judging by their online survey asking whether we want it or not, and how badly.)
Its creators apparently just partnered up with the Yahoo! Developer Network. This is exactly the tool I wish I had some day ago, when I dug up Dojo's getComputedStyle, to hack up a greased-weasel stand-alone getStyle which should be portable across browsers.