This is a pretty cool tool: Kip is basically a nice, iPhoto-like interface to a library of PDFs. It includes a tagging system and supports a scanner for adding all those bits of paper that you think you might want to keep but don’t want to put in a file box—So it could act like a sort of Delicious Library for receipts, correspondence, etc. Well, if I had a scanner. As an added bonus, it syncs with .Mac, too. That’s pretty cool. If it did BibTex—for instance, could read my BibDesk library—then it would be way cool.
(zooooomr)—You get a little preview window, with tags, when you mouseover a PDF.
Update: Kip is now called Yep, and will cost $50 when September rolls around.