SparkFun's minimal design approach to Arduino. This is a 5V Arduino running the 16MHz bootloader (select 'Arduino Duemilanove w/ 328' within the Arduino software).
This is a 3.3V Arduino running the 8MHz bootloader, in a very small package - a Mini Arduino, you might say!
You need to wedge an Arduino into a really tiny spot? Simple - just use a SMD '328 IC. Oh... you want a reset, and voltage regulator too? Why didn't you say so!
This is LilyPad Arduino, the heart of a wearable electronics system! This main board features a ATmega168V preloaded with Arduino, and is ready to connect to a wide variety of wearable, sewable modules!
Need space to add custom circuits to your Arduino MEGA? Here's the open proto shield!
This is just the PCB for building the MEGA Protoshield
This board mates directly with the Arduino USB board and allows the Arduino to wirelessly communicate over a modified ZigBee protocol using the popular XBee module from MaxStream.
Sometimes a gentle "beep" and "boop" isn't enough from a microcontroller. The Adafruit Wave Shield adds these audio capabilities to your Freeduino SB / Arduino!
Intertoobs. Intarwebs. Series of tubes. Whatever. Connect your Arduino / Freeduino SB to your LAN, WAN, or whole darn Internet!
The Sparkfun Arduino protoshield as some very useful portable prototyping space that plugs onto the top of the popular Arduino / Freeduino SB.