App Composer is a little tool that lets you package Mac applications for the Mac App Store with little hassle. We plan on updating it to potentially support more features and platforms. Comes with an update system. Download | Sample Entitlement
Networking extension for Windows, Macintosh and iOS. Permits online connectivity for GameMaker developers. Fully open source, modify it and pass it on!
Physics extension for PC, Mac, and iOS. Full implementation of Box2D, with portability and speed in mind. Use it when you need something a bit more accurate for movement in GameMaker.
Access the terminal from your GM4Mac app. This app, when used properly, can do a lot of things: just research the command appropriate to your needs.