Microlite20 is a free role-playing game containing character generation, combat and rules for magic, monsters and level advancement. I’ve ripped the guts out of d20 leaving just the essence of the game. Skills are much simplified, there are no feats and combat is as simple as it gets.
If you want a fast and light game that is small enough to print off and stick inside the cover of Dungeon magazine for your next session, read the CoreRules or download d20 Microlite and give it a try.