MacOS
From BetaArchive Wiki
Apple Mac OS X is the operating system for Apple Macintosh computers on the PowerPC (PPC) and Intel x86 platform. The latest version of OS X is Snow Leopard, Build [Enter Build Here]
Known versions
Developer Previews
Rhapsody Developer Release 1 Mac OS X Developer Preview 1, 2, 3, 4
Public Beta
Mac OS X Developer Preview 1, 2, 3, 4