Meteorologist is a free weather program for OS X. It allows users total control over their weather viewing, including simultaneous interlaced weather reports from multiple weather servers, multiple weather locations, weather alerts and much more.
A collection of open source and public domain software for Java, XML, and Cocoa, primarily. Some projects: ThreadWorker, Xmlizable, Base64, Tabu Search.
Appscript is a high level, user-friendly Apple event bridge that allows you to control scriptable Mac OS X applications from Python, Ruby and Objective-C. Appscript makes these languages a serious alternative to AppleScript for automating your Mac.