There's a large supply of classic DOS games available at abandonia.com
Using DosBox is easy once you get the hang of it.



Gamershell also appears to have a large supply of full games.
Fullgame Download Archive - GamersHell.com

MoFunZone.com also has alot of free games although most of them are merely demo's.

Postal 2 Multiplayer is also free although i believe the (game was banned in Australia due to it containing extreme violence and a lot of adult themes).
Full Games: Postal 2 Share The Pain Multiplayer Full Version - Demo Movie Patch Download Section - GamersHell.com

Assault Cube is a free online First Person-Shooter.
AssaultCube


Hope someone will get to use this quick list.