Here's the perfect, low-cost way to introduce 2.4 to your arsenal. This short-range combo is great for park flying and indoor flying models, or robots that will be operated within 100 yards line of site.
SparkFun's minimal design approach to Arduino. This is a 5V Arduino running the 16MHz bootloader.
The HD2 tracked platform is a large, heavy duty tracked robot with the power to pull a truck and climb stairs. A wealth of internal space allows for batteries, controls and an optional computer. Customized version of item TP-200-001.