Battery Mart Robot batteries and chargers
Nuts and Volts Magazine featuring electronics and robotics
Radio Shack Basic electronic supplies.
Diverse Electronics Services Motor controller electronics
Tech America Parts, test equipment.  Phone orders accepted.
JK microsystems Embedded DOS computers and ethernet industrial controllers.
Small Parts, Inc. Mechanical robot parts.
Robot  Robot Kits, Robotics, and Toy Robots
Robotics FAQ Contains great stuff on every aspect of robotics including information, parts sources, etc.
Military Robots Robotics at Space and Naval Warfare Systems Center -- Many cool robots!
Mouser Extensive electronics supply.
Digi-Key Electronics supply & great service.
Electronics Huge electronics site
The Guru's Lair Don Lancaster's site as advertised in Nuts & Volts Magazine.
Interfacing the PC Great info for interfacing  parallel, serial, & USB ports, interrupts, etc.