Article in today's WSJ (paid registration req'd). Sounds a lot like what Bluedot does. Mentions IBM's Dogear.

Quoted: With social-bookmarking software, when you find a page that's worth keeping, you click on the bookmarking button, and a window pops up that allows you to create whatever tags you want to assign to that document. The idea is to identify files with words that reflect a document's meaning to you, even if the term isn't in the document itself. For one document, it could be "Project Overseas," "India" and "call center." For another, it could be "Project Overseas," "Romania" and "software."