Jesse van den Kieboom
This little project took the webdavhandler ruby gem and adapted it to allow for any number of virtual file system implementations. This means that you, for instance, can have a webdav service which serves a file system residing in a MySQL database. Really anything with a hierarchical setup, can be represented as a filesystem. This WEBrick servlet makes it really easy to implement a custom virtual filesystem based on a few functions (like copy, move, iostream).
One of the things missing in the webdavhandler gem is the support for locking (LOCK, UNLOCK). This has been added to allow OS X to mount the webdav service as read/write instead of read-only.
The source can be found on github: http://github.com/jessevdk/ruby-webdav-vfs. Included are examples of a MySQL based file system and a local file system.