After Google Code have released MacFUSE, an open-source Mac port of the FUSE mechanism. FUSE is now available for Linux, FreeBSD and Mac OS X. The next step is to get FUSE ported to Windows, which would make FUSE truly cross platform, and give developers the capabilities to write a file system once, and deploy it on all major platforms.
I have submitted a application to Sourgeforge.net to host the project. The port will be based on the Shell Namespace Extension facility in Windows.