High altitude balloons have been used to perform experiments and collect data from the earth's stratosphere for over 200 years now, but recently with the availability of cheap consumer electronics some universities and amateur radio groups have started using them to take pictures or videos at "near space" altitudes. For about $150 you can assemble a balloon, prepaid cell phone with GPS, and a used camera to take some pretty cool pictures from pretty high up. If you want better tracking and the ability to shoot video you can spend a bit more to get some truly amazing pictures and awesome videos, not to mention gobs of data that would make even the Mythbusters jealous.
Some balloon projects use multiple cameras so that they can take pictures both downwards towards the ground and sideways to see the curvature of the earth. Last month the Balloon Experiments with Amateur Radio group launched their BEAR-4 balloon with an Hi-Def camera. They got over 4 hours worth of wicked cool video, even though the camera was spinning like a top over Canada half the time. Check out the highlights:
The only thing cooler than seeing one of these things rise and then drop from the sky would be to see the Entry, Descent and Landing of a rover on Mars :-P