There has been a lot of buzz this week about Flickrfs the virtual filesystem for Flickr. Using Flickrfs you can interact with Flickr tags and photos just like your regular filesystem. A similar service is GmailFS which lets you mount a Gmail account as a large virtual filesystem. Both of these services are built on top of FUSE. FUSE makes it easy to build fully functional filesystems inside of a userspace program. Users can script and manipulate files just like their regular files. FUSE is now part of the main Linux kernel with release 2.6.14. Check out the list of other interesting filesystems built using FUSE. Of particular interest: WikipediaFS, SMB for FUSE is similar to Network Neighborhood, SSHFS, btslave to mount torrent files, and djmount is a UPnP AV client.