Arduino PCB etchable pdf
There's a single-sided arduino PCB that you can etch at home:

http://www.arduino.cc/en/Main/ArduinoBoardSerialSingleSided

A smaller alternative is the Really Bare Bones Board (RBBB), it's Arduino compatible and comes with design files:

http://www.moderndevice.com/products/rbbb-kit

Or, you could do without a PCB and go for a Paperduino:

http://lab.guilhermemartins.net/2009/05/06/paperduino-prints/