github: https://github.com/ThomasCX/defragfs
The defragfs project aims on file-system/directory defragmentation of the Linux operating system, it is (currently) file-system independent and only CLI, hope further development could bring the GUI and better functionality.
freede is a free defragmenter for linux filesystems. It has the ability to adapt the defragment algorithm to the current filesystem. A general move-defragger is included, and should work for all normal filesystems.
AutoDeFrag is a launcher for the standard defragmenter built into Windows 2000. The standard defragmenter does not support the ability to be scheduled, and therefore must be manually launched when required, once for each fixed disk in your system.