[kghite]

Accurate and low-cost 3D mapping can be obtained using the Microsoft Kinect. Search Kinect mapping online, and you will find hundreds of projects implemented on various robots. This sensor is extremely affordable in comparison to LIDAR (Kinects run at about $120), and was also provided free in the 2012 KOP if you still have it around. The Kinect is RGBD sensor, combining both color camera and IR depth feed, which makes it a useful tool for both mapping buildings or scanning objects into CAD in color.

One example of a simple mapping robot configuration using the Kinect would be to run the image processing on an onboard laptop (depending on your preferred programming language, you can look into various options such as the Mobile Robot Programming Toolkit, the Robot Operating System, or your FRC programming software) and use an Arduino microcontroller for input from other sensors and motor output. There are many other options, and some robots can be purchased as kits or fully assembled depending on your target price range. iRobot currently has a great mapping robot based on the Roomba for around $400, but price can vary greatly depending on the complexity of the robot and how much of the system you are willing to develop on your own.

*edit* If you are looking specifically for a quadcopter, take a look at the A.R. Parrot Drone.