Here's a tutorial (by request) for people who want to try this out.
Remember, hydrogen peroxide is very nasty stuff. If you get it into your eyes, they will break. So don't.
Use protective goggles and wear rubber gloves. It's highly abrasive, and will bleach and irritate your skin.
Also, use common sense. Place the mixture where no kids or pets can get at it.
1. Buy some hydrogen peroxide (3%-35%). I can only vouch for 10% and stronger, since that is what I use.
2. Buy some Vanish Oxi-Clean.
3. Buy a UV-light. I use this one http://www.velleman.eu/distributor/products/view/?id=381476
4. Get a clear glass/plastic jar or bowl.
5. (Optional) Get a cardboard box and place some aluminum foil in it. I'm actually not sure the foil works, since the glass will probably reflect a lot of the incoming light from the foil. But I think some gets in, so it's probably not entirely useless (I kinda doubt household glass bowls are UV-treated). The cardboard box is kind of useful though, since you will need to stir the mixture from time to time, and it will soak up some of the mixture which will otherwise splash onto other things.
6. Dilute the hydrogen peroxide to 3-12%. I use about 10%. The weaker the mixture the longer the process will take.
7. Take a dash of oxi-clean (not much! The retrobright wiki suggests a 1/4 teaspoon per 500ml 10-15% hydrogen peroxide) and dissolve it in some warm water.
8. Place the keys in the bowl and pour the diluted hydrogen peroxide over them, make sure they're all covered.
9. Pour the warm water with the dissolved oxi-clean into the bowl. Stir.
10. Place the bowl in the cardboard box and light the entire thing with the lamp. Keep the lamp 30-45 cm away from the bowl.
11. Wait a couple of hours. Stir.
12. Repeat 11. until you're satisfied with the results.
13. Rinse the keys THOROUGHLY in water.
Also, make sure to use gloves or rinse the keys thoroughly before handling them to check intermediate results!
Apparently, only oxygen is released from the process. So it should be safe to put the thing pretty much anywhere. Don't take my word for it though, I am no chemist.
Been going a bit nuts with retrobright the past couple of weeks, here are the keycaps of a heavily yellowed G80-1000 after a couple days treatment! The case of the G80-1000 is still untreated. Look at the spacebar to see the difference. A non yellowed G80-1800 with the same type of keycap (doubleshots) was photographed with the same settings for reference. This stuff is truly amazing!
The pics look a bit weird (I think the white balance is off?), but I didn't want to do any Photoshop magic to them, just concentrate on comparing the keycaps of the upper and lower board.
Next up: this heinous thing