BurgerSpace

BurgerTime clone for Linux, Windows, Mac, or BeOS in which you are a chef and must collect ingredients to make burgers.
http://www3.sympatico.ca/sarrazip/dev/burgerspace.html

The Adventures of Jason

Java platformer in which one or more players jump around in a rectangular world, trying to catch stars and shoot each other. [Open Source, GPL]
http://javagame.sourceforge.net/

Adventures of Johnny Jetpack

Guide Johnny through his 3D world of platforms and lava to collect all the coins. (Open Source)
http://www.johnnyjetpack.net/

Ladder

A classic ASCII based arcade game similar to Donkey Kong. (Requires the Java runtime environment.)
http://ostermiller.org/ladder/

Super Pooch

A scrolling platformer for Windows similar to Super Mario.
http://www.geocities.com/jamez1988/pooch.html

VideoToons

Multiplayer Java platformer. [Open Source, GPL]
http://videotoons.sourceforge.net/

The Adventures of Toekan

A platform game for Windows with five different enemies.
http://www.darthy.f2s.com/products/toekan/

TurboLode

3D derivation of the game 'Lode Runner' for Windows with a real time stereoscopic mode.
http://eicart.free.fr/turbolode/

Robot Battle

An evolving programming game that allows players to design and build intelligent robots using a simple scripting language.
http://www.robotbattle.com/