I learned how to do this trick in one of the tutorials on nehe.gamedev.net: there are a bunch of cool OpenGL tutorials there.
First of all, go see Red Dragon. It's really, really good. It's far better than Hannibal, which I really didn't think was all that good. And, I think it might actually be better than Silence of the Lambs, though it's been a long time since I've seen that. Anyway, it's great. The villain is complex and pretty believable. There's one predictable Hollywood Cliché at the end, but it doesn't really detract. Second, check out my new screensaver. Imagine it, like, moving and stuff: glowy vapor trails and shifting transparent fields bleeding off an object bouncing around in 3D. What it does it, draw a cube and a few line segments; then render the whole scene into a texture; then repeatedly render increasingly-enlarged and increasingly-transparent versions of that texture back onto the scene itself. That produces the blur. If you don't have a good video card, it'll really hurt the machine bad: on one of my machines that is doing GL in software, it make the mouse stop moving for like 5 seconds at a time, though I get about 10FPS on a Matrox G450 at 1280x1024. (It'll be in the next xscreensaver, but turned off by default, which will be out probably some time in the next few weeks.)
Current Music: Gorillaz -- Man Research (Clapper) ♬