Mercury Playback Hack Premiere Pro CS5

Adobe's Mercury Playback Engine leverages the GPU of select display cards to deliver real-time editing. Pretty cool.

This video demonstrates the performance gains of the Mercury Playback Engine

Unfortunately the only display cards to be certified by Adobe are pretty pricey.

Here's an article that explains how to tweak Premiere Pro CS5 to work with cheaper NVIDIA cards. The changes look fairly simple although make sure to review cooling requirements as the demands on your display adapter will increase substantially.