paq is a family of archivers with the best lossless compression ratios now
available across a wide variety of test data, according to several benchmarks.
A comparison of paq to other compression methods, on a 2GHz T3200, when
compressing a large text file:

Format		Size		Time (sec)	Memory
				comp	decomp
-----------	---------	--------------  -------
Uncompressed	3,152,896
compress	1,319,521	1.6	0.2	 .1 MB
gzip -9         1,022,810	0.7	0.1	 .1 MB
bzip2 -9	860,097		0.6	0.4	  5 MB
p7zip (7z)	824,573		1.5	0.1	195 MB
xz -6		822,016		?	?	  ?
zpaq c1 (fast)	806,959		2	2	 38 MB
zpaq c2 (mid)	699,191		8	8	112 MB
zpaq c3 (max)	644,190		20	20	246 MB

The port uses the open ZPAQ specification, and contains: a public-domain C++
API for reading and writing ZPAQ compressed data to or from files or objects
in memory; serial and multi-threaded archivers;  extra preprocessors for
compression; and stubs for creating self-extracting archives.

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