Sparkfun A manufacturer and supplier of hobby electronics. Good tutorials and active forum.
Pololu A manufacturer and supplier of hobby electronics
AdaFruit A manufacturer and supplier of hobby electronics
Servo City A supplier of all things related to servos
Parallax Corp Makers of the Basic Stamp
Mondotronics Robot Store A reseller of kits and parts
Lynxmotion Robotics Hardware A manufacturer of robot kits both ground and aerial.
OSH Park PCB manufacturer.
Dirty PCBs PCB manufacturer.
PCB123 Board Schematic and Layout Software (FREE Downloadable Tools)
ExpressPCB Board Schematic and Layout Software (FREE Downloadable Tools)
PCB Assembly and other production.
Arduino Home page Open source software and hardware for Arduino based processors
Raspberry Pi Open source software and hardware for Raspberry Pi based processors]
Seattle Robotics Seattle Washington. Good website but no longer being updated. Fairly active email newsgroup.
Robot Club and Grill Used to run a robot fighting club around a restaurant. Archive only.
Trinity College Fire Fighting Robot Competition Run a maze, find a 'fire' and then put it out. Multiple classes for different age and skill levels.
Sparkfun Autonomous Vehicle Competition Race your ground vehicle around a course mostly for bragging rights. Held in Boulder CO, in June.
FIRST LEGO League Competition for 9-14 year olds using LEGO Mindstorm kits.
FIRST Robotics Competition Competition for middle and high school students.
Micro Mouse Build small robots to run a maze at blinding speeds. This Wikipedia page gives links to various organizations that run competitions.
Blogs or websites of interest
Hackaday Electronic project news aggregator
Dangerous Prototypes Open source hardware projects
Robohub Robotic news aggregator
EEVBLOG Watch the crazy Aussie guy talk about electronics. (5 stars)
Mike's Electric Stuff Watch the crazy British guy talk about electronics. (5 stars)
Applied Science Watch the crazy Californian do experiments including buildings his own scanning electronic microscope. (5 stars)
Instructables User submitted instructions/tutorials on wide ranging projects (recipes to rocket ships)
Soldering Basic guide to soldering
Misc. Robot Links
NPC Robotics Leaders in DC Motor Design
Engineering Services Inc Consulting Company specializing in custom robotics systems for industry, medical, and military applications.