I think it would be best to minimize the threads about free games by consolidating them into one thread (we've already had 3-4 threads about gunbound).

These are all free games available for download:

Gunbound
This has become a very popular game. A Korean version of Worms is the best way to describe this game. You, however, only conrol one character and can choose from a variety of vechicles with their weapons.
Note: You can pay for additional features.

Soldat
Soldat is a 2D shooter, offering a gameplay mix of Worms, Counterstrike, and old-school shooters ike Contra.
Note: You can register (costs a small fee) for additional features.

Survival Project
I have yet to play this. You can ask Cyndaquil about it in his thread.

Puzzle Pirates
Haven't had much experience with this game, but it involves playing several puzzle games to accomplish various activities (sword fight, find treasure, etc.) and goals. It also takes place in a persistent world, making it an odd cross between a MMORPG and a Puzzler. And it's got pirates.

Fairyland
This seems to be a MMORPG, but I have yet to play it.

Shattered Galaxy
A Massively Multiplayer Real Time Strategy Game. It looks like you can level up your abilities and units as you progress. You can engage in PvP battles or just tackle computer opponents.
Note: You can pay for bonus features such as extra exp.

America's Army
Regardless of recent events, the United States is still proving to be the coolest government on the block by making its own video game. This is a basic FPS in the mold of the US Army.
Warning: Though free, this is obviously a recruitment tool. So don't be surprised if certain aspects of the USA are in a very positive light.

Tribes 1 & 2
These two games are legendary in the FPS genre, and the company has recently released both for free.