SweetFX pc program -- add color and detail to games
Installing SweetFX can make the game look crazy better by pumping up the sharpness and colors and things. Here's Age of Conan.
I saw a thread somewhere the other day that had a large collection of before and after thumbnails for a bunch of different games but can't find it quickly now. Some of them don't gain much, while other games look ridiculously better.
Here's the official thread with plenty of before and afters in there. It's not the thread I'm thinking of though that had an entire page of before-after thumbnails.