Just like Citeseer and Google Scholar, but better! Rexa is at core a search engine for the computer science literature, but with additional functionality beyond what the others offer. The key improvement is that Rexa knows about more types of data than just papers — it can also track people, for instance. It also has w00ty Web 2.0 tagging, and a dodgy .info domain. If they only had rounded corners and a day-glo colour scheme they’d be a dead cert for an acquisition.