Backshift is a deduplicating (variable-sized, content-based blocks), compressing (xz or bz2) backup program. Full saves and incrementals are pretty indistinct other than the amount of data transmitted, somewhat like with "rsync --link-dest" but without the huge number of hardlinks. It also de-duplicates large file content at a granularity of about 2 megabytes on average; there tends to be a unique copy of each file with size less than around 2 megabytes on average.
pyReScene is a tool that recreates original RARs by backing up the metadata. It is a port of ReScene .NET to Python. It provides a mechanism for backing up and restoring the metadata from "scene" released RAR files. RAR archive volumes are rebuilt using the stored metadata in the SRR file and the files extracted from the RAR archive. pyReScene consists of multiple related tools: pyReScene Auto to create a complete SRR with one simple command, pyReSample to recreate sample files, and pyReScene Usenet to create SRR files on the fly from Usenet postings. Lots of other small scripts for managing SRR and SRS files are available too.