The Darwin Source repository is intended to fill a void left by the closure of the OpenDarwin project: providing a permanent and public repository for the open source components of Mac OS X.
DVD/CD UDF disc drive tools, esp. for the Iomega RRD (aka Iomega REV) drive. Usability patches for UDF mkfs and fsck. Commentary for the lk MMC and UDF source code. cvs co tarballs for firewalls that defeat CVS. Links, FAQ's, troubleshooting hints.
The Extensible Versioning File System, designed for Windows, Mac OS X, and Linux, introduces native versioning file system functionality to your operating system.
Xenu is a open-source/Apple public source project aimed at adding Xen Virtulization to the XNU kernel. Allowing users to run other operating systems and architectures binaries under Mac OS X.