Looking for the smallest Atmel microcontroller with built-on motor drivers? The BittyBot MEGABitty microcontroller features an Atmel ATMega8L, motor drivers, and voltage regulation in tidy 0.9" x 0.9" package!
This is a handy AVR programming cable that incorporates both the 10-pin and 6-pin ISP programming interfaces.
With the GPS Shield you can add GPS functionality to your Arduino.
Just need to make some motors move with your Arduino? Here's a simple way from SparkFun - the Ardumoto!
The Voice Shield™ (VS) is an analog audio shield for the Arduino that allows you to play audio sound byte.
This is a 7-segment shield for Arduino NG/Diecimila/Duemilanove and many Freeduino boards.
The Joystick Shield sits on top of your Arduino and turns it into a simple controller. Control man, get some CONTROL! (PCB only - buttons/components not included)
The Atmel ATMega168 is the heart of the popular Open-source Arduino microcontroller project. If it's good enough for them, it most likely can manage your project too!
This unit is a higher-capacity version of the ATmega168 - more than TWICE the flash memory for sketches (30K available instead of 14K), TWICE the RAM (2K instead of 1K), TWICE the EEPROM (1K instead of 512b)