PreComp utility
Current version: Precomp v0.4, lprepaq v1.3, paq8o8pre v2 (21.03.2009) - Main site
German Wikipedia DVD basic version without images from here
Tested with a developer version of Precomp 0.4 in slow mode, but the results should be the same for the release version.
Detailed results page - thanks to M.R. for this results.
From Maximum compression benchmark
|UHArc+0.6b+(837,997+bytes)|Precomp+v0.4+and+UHArc+(686,746+bytes)|lprepaq+5+v1.3+(698,584+bytes)
&chco=0000a0,0000ff,00ff00,008000
&chds=0,842468
&chxt=x
&chxl=0:|0|100+%
&chtt=A10.jpg)
From Maximum compression benchmark
"Official" test-suite for PNG
From here