I'm new here and probably won't visit often, but I thought I would share my site with everyone as it seems to fit into this category. For anyone who's interested...www.solar-balloons.com
Solar balloons are basically hot air balloons filled with ordinary air, which is heated by the sun. The material they are made with is usually black, which absorbs the heat from the sun and in turn heats the air in the balloon. I have released quite a few and my farthest flight yet was over 700 miles. Currently I make them all with the cheapest (thinnest) trash bags and masking tape...you can't get cheaper than that! Once they get up in the air, the sun keeps them heated for the rest of the day, and they cruise in the jetstreams at altitudes up to 50,000 feet until the sun sets and they make their way back to the ground.
If this sounds interesting, check my site out, and spread the word. Solar balloons aren't very well-known yet so I'm throwing it out to places like this.
Thanks!
PS - I hope I posted this in the correct forum, sorry if it's not