LEGO MINDSTORMS NXT (A LEGO Product)
MINDSTORMS NXT 2.0 is a robotics kit to introduce robotics in early age. It features the latest in robotic technology: an advanced programmable microcontroller, interactive servo motors, smart sensors, icon-based drag-and-drop programming software, interactive challenges, and wireless Blue tooth and USB connections -- all the smart technologies you need to create your custom robot. NXT, an intelligent, computer-controlled LEGO brick that features a 32-bit microprocessor, a large matrix display, input and output ports, and a speaker.
Robotic Kit comes in two version - educational and retail. The two kits differs in terms of number of components, while NXT brick remains same in both the kits.
Competitions Held - World Robot Olympiad (WRO), FIRST LEGO League (FLL) and FIRST Tech Challenge (FTC) are most popular competition organized on MINDSTORMS kit.
You can buy MINDSTORMS from LEGO, Amazon, or other online / retail source based on your country.
Link - http://mindstorms.lego.com
TIP: Good for beginners as it comes cheaper than VEX