Hello World,
This post is about quadrotors:
AeroQuad is an open source quadrotor project.
Here is a video of A Swarm of Nano Quadrotors, and Aggressive Maneuvers for Autonomous Quadrotor Flight.
Here is a video of a MK Mikrokopter looping.
Here is a list of Quadrotor, Kits and Parts, Drones For All Tastes and Budgets.
DIY Drones has quadrotors and other UAVs. They are also responsible for Arducoptor, an Arduino-based autopilot for multirotor craft. uDrones offers an ArduCopter 3DR that is ready to fly.
Robbe Modellsport offers the RO-Coptor P-Frame and RO-Coptor A-Frame.
Draganfly offers the Draganfly X4.
AscTec makes the Hummingbird.
Quadrotor shopping list
1 frame