Sorry, perhaps I should explain my original post a little more clearly. I was just planning to buy parts from any of the sites, probably Spark Fun, listed on this site, but I just don't know which specific parts to buy. I need to know how to choose sensors, chassis, shield, motors, wheels, etc. and then how to put them all together. Can you recommend any tutorials? Eventually I want my robot to be able to drive around, avoid obstacles, manipulate small objects, switch from an AI to a remote control mode, etc.
So, basically, I don't need to know where to buy parts, I need to know how to choose them and how to put them together.
EDIT: Actually, the Robot Shop link was very useful, thank you! (But I'm still looking for a tutorial on choosing and building.)