..Great books about using and programing the Arduino
Getting Started with the Arduino (A good beginner's book.)
The Arduino Cook Book 2nd edition (A Must Have, it's a Great Book!)
All of The Code from The Arduino Cook Book 2nd edition.
Making Things Talk ( A great book about connecting the Arduino to the world.)
Making Things See (A great book about using the Arduino with the Kinect sensor and the Processing language on a PC, MAC or Linux computer.
Making Things See website.
It's easy to use the Processing language on your computer to work with the Arduino.
The Official Processing language website.
Electronic parts sources for your projects..
Sparkfun (lots of good stuff.)
AdaFruit (Lots of good stuff and great tutorials.)
(Home of the BASIC Stamp, Propeller and a lot of great robot kits, sensors and Arduino support as well.)
Seeed Studio (low cost open source Arduino based boards and shields.)
Servo City (A great place for servos and accessories.)
Tayda Electronics (really inexpensive electronics.)
Market Place (Robotic combat tested products,
Ya we have tested this stuff, HARD!)
HobbyKing (Arduino clones. Very inexpensive like $18.00 for a MEGA 2560!)<Good Deals!
Robot Shop (lots of robotic parts.)
Trossen Robotics (lots of robotic parts and sensors.)
Electronics (Major electronics supplier.)
Newark Electronics (Major electronics supplier.)
Ebay (a great source for parts, just search for Arduino.) A note about Ebay: A lot of the sellers only sell Arduino Clones that claim to be Official Arduino boards. They may still work fine, but you should be aware of this when ordering... Also some of the stores are actually based in China so shipping cost's and shipping times will vary. For an example I recently ordered some Bluetooth boards and it took about 1 month to get them on the West coast of the USA. The parts worked fine but you have to be patient when using standard shipping..
I actually wrote this cover story about my bartending robot, Brandy's Bar. ^^^
Magazines and Publications.
filled with great information and parts
Brandy's Bar. My bartending Robot. Touch screen PC/Arduino based, programed in Processing.
Team K.I.S.S. Robotics!
Keep It Simple Stupid.