Michael McCracken is pimping a new app by Christiaan Hofman: "Skim"

"Skim is a PDF reading and note-taking app for Mac OS X that is designed to make reading research papers and manuals better. Just like in Preview, you can search, scan, and zoom through PDFs, but you also get some custom features for your workflow"

It's brought to you by the same guys who did BibDesk.