US / Canada East Coast

RobotShop - very wide variety of robot parts, fast handling

Adafruit - specialty products - Arduino shields

US / Canada West Coast

pololu - very wide variety of robot parts, fast handling

jameco - great electronics source, good selection of robot parts, fast handling

Sparkfun - Lots of cool stuff

ASIA

dfrobots - wide range of robotics, great wiki on robotic parts

 


Useful Parts

I/O Shield for Mega - Easy way to connect tons of stuff to Mega 2560

Use these to build cables for the I/O shield:

Wires with pre-crimped ends - These plus the next item let you make your own custom cables with connector

Crimp connector 1x3

 

I2C Stuff: - I2C is great when you need to connect a bunch of items to your Arduino

3v to 5v convertor for I2c - Let's you use 3v and 5v items on same I2C bus

I2C bus - simple extender gives you 4 I2C connectors (using Grove connectors)