Before I moved out, I was working on a project to convert my white 360 accessories to black. They sell the basics in black, but the Vision Camera, the Messenger kit, the battery charger, and the wireless headset are all a mismatching white.
I'll be honest, I haven't even purchased a black battery yet. One of these days when I have a few bucks to waste. However, the messenger was the white accessory that bothered me the most.
Following Alacron's directions, I grabbed some plastic bonding paint from the store. They didn't have the Plastikote in black that I wanted, so I ended up wiht Krylon Fusion, which seems to do the trick. Anyway, he's right; take it slow and only do a light coat each time. The great thing about Fusion paint is it dries in about 15 minutes, so you could get the paint job done in a day.
Holding the can away 8-10 inches and doing a light pass is critical. You won't get it solid black until 3 or 4 passes if you are doing it correctly. Even then, a couple more coats won't hurt. Just make sure it dries and stay light so it doesn't run.
Again, we're waiting on pics. But I've done my memory card; it looks great, and my Messenger keyboard. It looks immensely better than white on black. I'm doing my Vision Camera right now (look for 6 screws on the bottom, underneath the label sticker and the rubber ring). I think I'm going to be happy with the results.