When my laptop disk started to show read errors I searched for a tool capable to save the contents of the disk (multiple systems on it with different file system types). I couldn't find anything which would do a copy of the disk skipping unused areas and tolerating I/O-errors, so I ended up in re-installing all systems after I got a new disk.
The ideal solution would be some clever combination of dd_rescue and tar which could be put on a live-CD like gparted and be able to save the disk in question. To save a 500GB disk with 200GB data on it the tool should require only some 200GB of empty disk space, not the full 500GB of the physical disk to be saved.
The goal of the project is a program doing a disk copy by saving only the used blocks. It would read the partition table and handle each file system by an own plugin (e.g. a swap partition wouldn't be saved at all).
This project is one of its kind!