Step 3: Gather Components
Here are the parts you need and the digeykey part numbers. For items that don't have a minimum of 10, I recomend you get at least 2 and possibly more. If you have 2 good boards, you can make two Ardunio Compatibles. The small parts are really, really easy to lose so having extras is great. Be careful with them when you open the packages.
2x 445-6389-1-ND INDUCTOR MULTILAYER 10UH 0603
2x 490-1198-1-ND CER RESONATOR 16.0MHZ SMD
2x 754-1547-1-ND LED GREEN ROUND CLEAR SMD
2x ATMEGA328-AU-ND IC MCU AVR 32K FLASH 32TQFP
10x 541-10.0KSCT-ND RES 10.0K OHM .25W 1% 0603 SMD
10x 445-1316-1-ND CAP CER .10UF 25V X7R 10% 0603
This bill of materials costs about $15 + shipping at the time of this writing. If you know what you are doing you can make substitutions. All these parts are really standard. Don't substitute the Atemga328 chip unless you are super sure you know what you are doing. This one works, I promise. If you get another I can just about promise the fuze settings I recommend turn it into a tiny coaster.
You will also need some standard headers and some right angle headers. I like long headers so you can push them into a breadboard and still put female jumpers on the top.
18 x Standard long Headers
12 x Right Angle Headers
Optional External Voltage Regulation
2 x P5149-ND 22uf capacitors
1 x IFX25001TS V50-ND 5.0V 400MA Voltage Regulator
I have tested this regulator in a bread board with 12v "wall warts". It works great and it has a lot of built in protection. It also has plenty of power to run your Atmega chip and lots of other stuff besides. Remember not to source more than 150 MA directly from your Arduino pins. (That's about 7 LEDs at full brightness.)