I bought Jane a $60 quadcopter from Banggood for her 10th birthday. One of the motor wires was broken on arrival so I had to solder it back on, and the battery charger was for a European power outlet so I broke it open and soldered on a US plug. Now it works and it's a lot of fun. It has a built in video camera, too!
It has two control modes. Mode 1 is the "beginner mode," which doesn't allow for tight turns. We like Mode 2, because it's actually easier to control. You can flip the captor 360 with the touch of a button on the transmitter, which Jane loves.
Here's a video of Jane flying it and me being paranoid that she's going to get it stuck in a tree. She ends up landing it in the street, and I say a naughty word.
The ETH Zurich quadcopter folks have added to their already impressive collection of videos of cooperative, autonomous quadcopters doing exciting things (previously) with this video of the adorable little gizmos throwing and catching balls together.
Cooperative Quadrocopter Ball Throwing and Catching - IDSC - ETH Zurich
To toss the ball, the quadrocopters accelerate rapidly outward to stretch the net tight between them and launch the ball up. Notice in the video that the quadrocopters are then pulled forcefully inward by the tension in the elastic net, and must rapidly stabilize in order to avoid a collision. Once recovered, the quadrotors cooperatively position the net below the ball in order to catch it.
Because they are coupled to each other by the net, the quadrocopters experience complex forces that push the vehicles to the limits of their dynamic capabilities
[Video Link] Here's a quadcopter video tour of a treehouse somewhere in BC, Canada. (Via Llyod Kahn's blog)