Powergame Home Page  
   Powergame is a free superhero RPG which has been in development since 1994. It is designed to cater for all levels of superheroic campaigns within a simple rules framework. There are currently two supplements available, and a new edition will be released
   http://www.uta.fi/~trmika/gameindex.html

Men & Supermen  
   A game distributed under the GNU Free Documentation License.
   http://www.hoboes.com/html/RPG/BrandX/

Super Heroes and Heroines  
   Designed to portray superheroes who have personal lives.
   http://members.tripod.com/~TrevorDoom/

Panels  
   Tabletop game which paints the world of superheroes in broad strokes. Numerically light, almost free form rules.
   http://www.geocities.com/Area51/Quasar/9229/supes/

Rumble  
   A simple and fast paced system with a large list of super powers.
   http://kevan.org/rumble.cgi?rules

Super Human High School  
   Game where players take the roles of ordinary teenagers who posses mutant powers.
   http://yekrats.com/dogtown/shhs.html

Risus Supers Version 1.1  
   Provides simple game mechanics to simulate superheroes who no one takes seriously. Includes character cliches and rules for common contests.
   http://www.angelfire.com/tx2/webgamer/supers.html