I worked at Feedster a few years ago. Now apparently it has sunk below the waves. It was an interesting idea with some great people, and a spectacular example of where having a bunch of smart people doesn’t necessarily mean you’re built for success. In responses to Richard’s question though, I use Technorati. Just about the only thing I do is subscribe to link searches though. Check to see who’s linking to my blog, or linking to AdMob. I rarely use the site itself or do keyword searches.