Self-made Arduino shield – making a PCB
Sooner or later, everyone bitten by Arduino bug would want to make his own extension. At the beginning Proto Shield may be sufficient.
When we have a working prototype, we might want to convert it into a series model, so PCB board will be needed.

On Arduino Forum there is a link to a very nice tutorial, how to make our own PCB board, especially for Arduino shields.
Aaron Eiche, author of the article is a member of DorkbotPDX group, which makes orders for PCBs and everyone can order with them the price is quite attractive – $5 for square inch of a double sided board + $15 for shipment (worldwide). It must be ordered in multiples of 3.
A little clarification here:
The $5/sq. inch gets you 3 copies of your board. It doesn’t need to be ordered in multiples of 3.
For instance, if you have a 2in.sq board, you’ll pay $10 and get 3 copies of the board. If you happen to be in the US, shipping is free.