CopyFS aims to solve a common problem. Given a directory full of configuration files or other important files that can be modified, it ensures that a backup of a file will be made before modifying it. This filesystem is based on FUSE for Linux, and makes the whole process transparent, automatically keeping versioned copies of all the changes done to a file under its control.
Unionfs is a stackable unification file system which can appear to merge the contents of several directories (branches), while keeping their physical content separate. Unionfs is useful for unified source tree management, merging the contents of a split CD-ROM, merging separate software package directories, data grids, and more. Unionfs allows any mix of read-only and read-write branches, as well as insertion and deletion of branches anywhere in the fan-out. To maintain Unix semantics, Unionfs handles elimination of duplicates, partial-error conditions, and more.
phpXplorer is an file management system and explorer that makes it possible to work on a remote file system through a Web browser. By default, it includes dialogs for editing HTML, PHP, images, Apache, compressed files, and emails. Its modular design makes it easy to build your own filetypes, property sheets, views, and themes. A permission manager allows you to restrict access to the shared file system for multiple users in a detailed way.
ext3cow is a time-shifting filesystem implemented with copy-on-write (COW) and based on the very popular ext2/ext3 filesystem. It's a functionally-enhanced version of ext3 that allows you to take a snapshot of your filesystem with one second granularity, freezing the way the filesystem looked at given point-in-time. You can then travel back through time and be presented with a read-only image of the filesystem. It needs no special mounting or "." directories; just type a name or directory followed by the special "@" character and a time.
ptiotest is a tool that is intented as a testing tool for I/O performance. It basically creates a fixed number of threads (defined at compile time), and each one of them peforms several jobs, all involving I/O to disk. It basically simulates a load of processes writing, reading, and deleting data to a filesystem.