TOCC is a Tool for Obsessive Compulsive Classifiers. It implements a file system that uses tags instead of folders, allowing you to classify files however you want. For example, you could tag photos by location, people, and technique (e.g. black & white, HDR). Finding files is as simple as running a query like "give me all files tagged photo and my-love".
fstransform is a tool to change a file-system from one format to another. For example, it can change from jfs, xfs, or reiser to ext2, ext3, or ext4. It works in-place and without the need for backup. It currently has been tested on Linux only. It uses a sparse file to create the new file-system image, moves all the files of the existing file-system into it, then remaps the sparse file to the original partition.