Little Bits Electronics Kits – $29 – $149
The Little Bits electronics kits use modular components to teach how the components work, and magnets insure that stuff will go together correctly.
Toysmith Robot Kits – $10 – $20
Toysmith has all sorts of robot kit options, like the Tin Can Robot. Or the Brush Robot. Or the Robot Duck. Or even the Propeller Racer.
Maker Arduino Kit – $65
The Arduino is a more advanced controller kit, but it’s a very popular core for many robotics projects that will encourage learning programming as well as building.
LEGO Mindstorms NXT – $280
The LEGO Mindstorms NXT kit is the ultimate in robotic kits if you have someone on your list who’s really geeky! They’ll definitely need to know something about robotics for this one, but it includes everything you need to build a COMPLETE robot.