This Arduino that is sold by Tom Scarff is called 'boarduino' He ships quickly and is very reliable and responsive to silly questions by beginners. It's an ATmega168 microcontroller chip; analog 0 thru 5 pins; and comes preprogrammed with a "no-wait" Arduino bootloader 2 red LEDs, power and "pin 13" just like the Arduino Diecimila with a 16 hz clock (resonator) It has the 2-pin header for MIDI OUT.
The arduino source code is available on his site.
Step 1: Building a midi controller with the boarduino
So I turned to him for this project and found that he already had a kit (called a boarduino) ready to go.
http://midikits.net23.net/midi_boarduino/midi_boarduino.htm The Boarduino is interesting because of its size. It's tiny (.75" x 3.75") and will fit in a small spot and the price is good. I prefer to buy it assembled - one less variable.
The easiest way to get started is to put a 9v battery on the standard 2.1 mm. Here a word of warning. You need to keep the power source within spec. I left my battery plugged in over a week or so, it dropped down below 9v and the microprocessor (trying as hard as it might) lost its marbles. Fortunately one can re-upload the code and you are back in business.
You can also provide 5vDC to the serial pin or the board but be very careful as there is no diode to protect you for reverse polarity (as there is with the 9v external plug).