So here is the final product! The cat skull I had wasn't too stained to begin with, it was browned white when I started this: http://www.furaffinity.net/view/8463883/

But now it's a CLEAN and crisp ivory!
I tried a new method with this one, Oxiclean. I mixed oxiclean (Actually it was LA's Awesome Oxygen Cleaner I think, I got it from the dollar store) with water. The active ingredients in oxiclean create Hydrogen Peroxide.

I filled a ziplock bag with warm water and like 3 scoops of oxiclean and left this set in the sun for maybe 6-7 hours, The results were great!
This was also a very cheap, easy, and seemingly quick way to whiten bones!

Next step is to re-insert the teeth into this specimen.

The rest of the bones I started with are still outside whitening. I actually mixed peroxide with the oxiclean for some of the bones (Especially the coyote skull which had a dark stain near the cheek bone) Though the lower jaw on the coyote came out nice too! (I used peroxide and oxiclean to do those.

So start to finish, this skull took maybe a week and a half to finish, (This started with NO flesh I found it picked clean in an old school house, very old)