IconFactory's open-source port of UIKit to Mac, made for the most recent release of Twitterific. Very likely as awesome as twitterific, and a brief look into how industry pros write Objective-C in the large.

For when you want to actually get that app into the app store

Absolutely beautiful app for organizing academic papers.

Makes unix geeks weak in the knees, myself included. I'm glad for it every time I open a terminal.

Alex Chaffee presents a bit of unix magic to get the rjb gem to install under OS X