http://www.allelectronics.com/ absolutely great for anything electrical and lots of things that aren't. they have things not even they know what they are (I'm not joking either). rating: 5 stars (ive bought tons of things here)
http://directron.com/switches2.html nice for various neat switches. rating: 2.5 stars
http://www.superdroidrobots.com good for general robotics rating: 3.5 stars
www.supercircuits.com if you ever want to mount a camera on your robot and i recommend it go hear latterly the worlds best supplier. rating: 4 stars