So i took the time and wrote a tutorial (with some pretty pictures) on how to make a pair of tennis ball poi for under $20. I made 3 pairs for ~$15, because the tennis balls only came in 3 packs, so i had to buy two ~__~
anyway, heres the tutorial:
TENNIS BALL POI TUTORIAL PDF File (just for Sister Eleven
Use it, post it on a website somewhere else, give it to friends, do what ever with it!

obviously give me credit for it, but i dont care what you do with it.
have fun!
~Woodsy
_________________________
Woodsy:Down with the sound, and the people will all yell: "POWER IS MEASURED IN, DECIBEL".
Poje: not Joules?
Woodsy: No...Never