In of my first attempts to use the Arduino, I came across the CW keyer from K3NG. I was amazed by the possibilities Anthony had managed to put in his keyer.
I made my own version with a remote unit for the memories and the speed button. Equipped with some leds. The Arduino is build in a separate box. This can be placed behind the transceiver. Both units are connected by a small patch cable with RJ45 connectors. Although the unit is housed in plastic boxes no RF troubles.
The remote unit
The uprocessor unit
All information can be found:
http://blog.radioartisan.com/arduino-cw-keyer/
There is a yahoo group were you can get support. Problems are solved in a very quick and nice way.
You can download the keypad files HERE
You can download the keyer files HERE