I just ran across Fritzing, a FOSS application for diagramming your electronics projects. There are tons of common symbols, plus extras like the Netduino.

Here's a very quick Fritzing drawing of the circuit for the DAC test project.

Here's the automatically-generated schematic for the same circuit. It could use some work in layout, but not bad for something auto-generated.

I imagine you'll be seeing more from this application in my future Netduino and electronics posts.