A Program for Compressing Files
http://tukaani.org/xz/

The xz command is a very powerful program for compressing files.

* Average compression ratio of LZMA is about 30% better than that of
   gzip, and 15% better than that of bzip2.

* Decompression speed is only little slower than that of gzip, being
   two to five times faster than bzip2.

* In fast mode, compresses faster than bzip2 with a comparable
   compression ratio.

* Achieving the best compression ratios takes four to even twelve
   times longer than with bzip2. However. this doesn't affect
   decompressing speed.

* Very similar command line interface to what gzip and bzip2 have.