Today at preschool we made these:
We used clear glass ornaments from Target. Simply pull off the silver hanger part and set it aside. Then I helped the kids use a funnel to pour some glitter inside (optional). The kids picked two colors of acrylic paint and I squirted both colors inside. You have to aim down the inside of the ball, which might take a little bit of practice. You can use more than two colors, but too many will make it look "muddy." Then I gave the balls to the kids and told the to turn them slowly and watch the colors run around inside. (Truly, you can just set them aside and turn them every few minutes, but the kids liked watch the colors move and it helps them feel more a part of the activity.) I also wrote the kids name and '08 on the balls in silver or gold Sharpie. Set them aside for a day or two to dry out and then pop the silver hanger part back on. They will be gifts for my kids' parents. AWESOME!