Links to source code of Mac applications and smaller sample code projects, because it is considerably harder to find "real-world" Mac sample code than it is for iOS.
Please feel free to extend the list by forking and sending a pull request.
- TextEdit
- OmniGraphSketcher - Make elegant looking graphs in seconds
- Seashore - Image editor which features advanced tools like multiple layers and alpha channel editing
- Paintbrush - Cocoa-based paint program, similar to Microsoft Paint
- OpenEmu - iTunes for retro gaming
- iPulse - Graphically displays the inner workings of OS X
- Burn - Disc burning
- Adium - Instant Messaging
- Cheddar for Mac - a simple & instant task manager
- Hacky - browse Hacker News in a clean and minimalistic way
- Bean - a word processor
- GitX - need you ask?
- Pinna - an elegant, iOS-style music player
- Core Data Editor
- Facebook Messenger for Mac
- The unofficial WWDC app for macOS
- macSVG - An open-source macOS app for designing HTML5 SVG art and animation
- Rebel - a framework to make AppKit easier to work with, made by github
- JUInspectorView - a shameless copy of Xcode 5's inspector views