Binary download: MilkPack v. 0.7 alpha (ZIP, 13.3MB. Updated on January 31, 2010)
Source Code: http://github.com/edgargoncalves/MilkPack (Git repository, development branch. Subscribe to its updates.)
This open source project targets the average Remember the Milk user that lives within Mac OSX. It allows simple task management on a familiar Cocoa interface. (It's still in alpha development state!)
From the developer standpoint, the code is written in Common Lisp (I used Clozure CL, former OpenMCL, to allow easy access to the Objective-C frameworks). It also uses my RTM Lisp API library to access the remote task management interface. While this is my first project in Cocoa, feel free to take ideas from the code, or to provide any feedback you want.