I have just discovered this wonderful application for circuit-board development via a posting over at Szymon Kobalczyk’s Blog. Fritzing is a program that lets you convert your breadboard prototypes into a physical PCB. For more information check out the following video:
The official spiel goes like this:
Fritzing is an open-source initiative to support designers, artists, researchers and hobbyists to work creatively with interactive electronics. We are creating a software and website in the spirit of Processing and Arduino, developing a tool that allows users to document their prototypes, share them with others, teach electronics in a classroom, and to create a pcb layout for professional manufacturing.
In brief, you simply put all the components in the breadboard view exactly the same as you would do on your physical prototype. Fritzing will then compute your circuit board for you 
As a bonus CW2 over at the netduino forums has created a custom netduino part for the application so as far as I’m concerned this ones a real winner.