Anybody building/releasing hobby balloons...

Hi Folks, Is anyone out there building/releasing hobby balloons. Small (under 6' diameter) helium balloons with a note or something attached asking the finder to mail it back to you? Seems like I heard of a school somewhere doing this and receiving postmarks from all over the globe. Any info? THANKS!

Tim, I realize you said you were looking for helium balloons. However, I just ran accross this link the other day for hobby size hot air balloons.
http://www.overflite.com/overflite.html

yea ive found one out in the desert a couple of years ago i had travelled a good 40 miles id say. but it was a regular balloon so as it got vay up there it probably expanded enough to pop itself. to travel all around the world though? I once bought a big rubber weather balloon about 5 ft. id say. I bet one of those could go quite a long way if you inflate it half way( room to expand) and water proof the note ( in case it comes down in the middle of the atlantic)

Hi, I don't know if this will help or not but someone in my balloon email reflector group asked about tissue balloons. The suggestion was to try Edmund Scientific at www.scientificsonline.com The tissue ones are 12 foot and 9 foot. Good luck! Kimberly