One of the things I love about Google—and that drives me a little crazy—is that they're constantly coming out with so much cool stuff, both big and small, that it's hard to keep up with it all. I'm loathe to say impossible (since sites like Google Blogoscoped do a pretty bang-up job), but I'd rather spend my free time listening to NPR or playing cards than stocking up on Google press releases. So I miss a few things here and there.
Just last week I found out about Google Experimental: Google is constantly running experiments on their search pages, but usually you only stumble into them by chance (and often don't know you were in one until you think about it later and go "Wait a minute, did I really see [whatever] on that SERP?"). But apparently, with Google Experimental you can explicitly enroll yourself in certain experiments to try out new features that Google is testing for search. Cool, huh?
Looks like it's been in Labs since May. Apparently I live under a rock.