ZPAQ

http://mattmahoney.net/dc/zpaq.html

Great compression, but slow. The best feature is the possibility to add only the "diffs" to an existing compressed archive... maildir in my case.

Gzip like interface for ZPAQ

MZPQ

I have created a simplified, streaming compression only, version called mzpq. mzpq uses the ZPAQ compression library, without all the extented features of zpaq... just trying to be a drop-in replacement for gzip.

https://github.com/twekkel/mzpq