how to use tennisball another way

Is there a way to be green and play tennis? Can we recycle these yellow orbs in some useful way?
One way many of us recycle tennis balls is as toys for our dogs, but one Internet article ("50 Great Things You Never Knew You Could Do With Tennis Balls", easily accessible by typing the title into a search engine) says that tennis balls should not be used as dog toys since the felt covering can wear down a dog's teeth and larger dogs can choke on tennis balls.
Other standard uses include putting them on chair legs to cut down on noise and scuffs, putting them on walkers to make them easier to push, using them as a trailer hitch cover on trucks and placing them in the garage as a stop indicator (hang one on string from the garage roof to help you park without running into things).
My top 10 favorite uses for tennis balls listed on that site are more non-standard:
1. Athletes can improve their hand-eye coordination, visual reaction time and keep brains sharp by learning to juggle tennis balls.
2. Most tennis players have sore feet. We play through the pain, but tennis balls make wonderful foot massagers. When seated, put a tennis ball on the floor under each foot and then roll your feet around on them for relief from aching feet.
3. Tennis balls make a great safe or hiding place. Place money, keys or jewelry you want to hide inside a slit in the tennis ball.
4. A tennis ball on the end of a broomstick can clean cobwebs from the ceiling.
5. Many janitors use tennis balls to remove scuffs on floors.
6. Keep patio chairs from getting stuck between the slats of your deck by putting tennis balls on the bottoms of chair legs.
7. It has been said that some gnats or flies can be kept away while outdoors if you'll cover a tennis ball in petroleum jelly and hang it from a tree or bush.
8. Tennis balls can be used as cushioning when packing something for shipping in a box that's too large.
9. In the laundry they have many uses. To assist your dryer throw a few into the dryer to fluff comforters, coats, pillows, or anything else needing fluffing. Two or three in the dryer can also help a load dry faster.
They can act as scrubbers for shower curtains. Put your mildewed curtain, a tennis ball and one-half cup of vinegar into your washing machine and wash on hot. The vinegar kills the mildew and the tennis ball helps scrub the mildew off.
10. Tennis balls absorb body oils from people who swim in the water. A few floated on the water and replaced every few weeks can make cleaning easier.
Clarification
I need to make a clarification regarding my last column about the new Florida tennis license plate. My friend Bill Hebrock wanted me to make sure that tennis enthusiasts were not disappointed if they went to the tag office looking for the tennis tag on Oct. 1.
He correctly pointed out that although the law allowing the sale of tennis plates would be effective that date, many steps need to be completed before the first sale including final approval of the design required action by the governor and the cabinet. He advises tennis lovers to not look for a tag before February.