Monte Cook's Arcana Unearthed

Monte Cook's Arcana Unearthed is a "variant player's handbook" for the d20 system, published under the OGL license. Two years later, it was superseded by Monte Cook's Arcana Evolved, which included new and expanded material.

Links:

Official Sites

http://www.ptolus.com/cgi-bin/page.cgi?auhome

http://www.ptolus.com/cgi-bin/page.cgi?arcanaevolved

Diamond Throne Fan Site

http://diamondthrone.com/

Wikipedia

http://en.wikipedia.org/wiki/Arcana_Evolved

RPG.net Game Index

http://index.rpg.net/display-entry.phtml?mainid=1148