It has been a holy grail for many years now and it is very close. The ability to assign a drive letter to your linux filesystems under Windows.
I am doing some final tests on my first release of Virtual Volumes which includes support for Dokan. Dokan is the Windows equivalent of FUSE under Linux. This means you can implement a filesystem in a userspace application.
There are some knows issues but my Windows XP install test was successful and I am currently doing some large file testing. If all goes well I might get a beta version released this weekend.