Sparkle: automatic application updates
Here’s a very cool little open source module for Cocoa application developers: Sparkle by Andy Matuschak. It allows applications to detect, download, and install new versions automatically. It apparently can be added to a project without any glue code at all. It supports Appcast feeds. It’s got handy features like Skip This Version and Remind Me Later. It can work with .dmg files or .zip archives.
During my brief stint with Cocoa programming I really wanted something like this. As a user, I like it because it makes life on the bleeding edge much more convenient.