http://blog.wolfire.com/2009/04/post-processing-part-two/
I had a lot of fun the other day experimenting with post-processing effects, so I made a video to show how they look in action, and to explain how some of them work. While they are fun to play with, we will probably focus on them last — we want to make sure that Overgrowth looks great even without post-processing! However, if you pre-order, you will be able to try all these shaders in the next alpha. You can also change the shaders, and they will update in real-time.
Here is the video, click here for HD!