For Xbox cheats try teamxbox or IGN.
For PS2 cheats try GameSpot or IGN.
IGN also have an excellent strategy guide for The Clone Wars, it's for the PS2 version but should be relevant for all releases, you can find it here.
The below cheats are for the GameCube release:
To enter a code, select 'Options' on the main screen, then choose 'Bonuses' and then 'Codes'. After successfully entering a code a confirmation message will be displayed at the bottom of the screen.
- ' 1WITHFORCE' Gives you invincibility, under extreme attack you may still take damage. Change player or reset GameCube to clear.
- ' GASMASK' Enables access to all levels in campaign mode (single player).
- ' FRAGFIESTA' Enables access to all multiplayer levels.
- ' CINEMA' Give access to all FMV sequences. View them from the bonus menu.
- ' CHOSEN1' Unlimited secondary ammunition, you need to re-enter the code after every mission.
- ' YUB YUB' Will mark the bonus objectives as complete for the mission following the one you just completed, i.e. if you have just completed mission 6 then enter this code, mission 7 will automatically have the bonus objectives completed.
- ' SAYCHEESE' Unlocks team photos in the sketchbook, you must already have access to the sketchbook to see the photos.
You can unlock extra players for the 'Academy' multi player levels with the following codes:
- ' ROGERROGER' : Battle Droid
- ' CORDE' : Amidalla
- ' WAT TAMBOR' : Super Battle Droid
- ' FUZZBALL' : Wookie
Earning bonus points throughout the game gives you the following items:
- 5 points : Raxus Duel multi-player map
- 10 points : Thule Moon Control Zone multi-player map
- 15 points : Rhen Var Conquest multi-player map
- 20 points : Jedi Academy multi-player map
- 25 points : Unit viewer
- 30 points : 'Making of' video
- 35 points : 'CD Player', listen to the audio tracks in the game.
- 40 points : 'Sketchbook', work in progress art etc..
- 45 points : Play as Yoda in the Jedi Academy multi-player map.