Games whose modding community allow great content creation?

I'm not cut for development, but I am willing to contribute with assets, because it's the closest that I can get to game design. I want to try those that I can play beforehand, to get a feel for what they are, when I could design for others. My PC is not updated though. I will have to select those which I can run.

Try Warcraft 3 or Starcraft 2.

@darktruth007: Warcraft III is great, I agree with you

@Valkeerie: People still make mods for the original D00M and D00M II.

Otherwise if you're into 3D modelling The Elder Scrolls series seems to have large modding communities.

I have Warcraft 3 on disc. I will install it. What about Free Space 2?