If you need some open source PCB Layout Software – maybe for some open source work – Fritzing can be fun.
It runs on Windows/Linux/MacOS. The linux version has a warning that is tested only on Ubuntu LTS 10.4.2, openSUSE, Fedora- via yum, Debian.
The windows archive is only 18.6 MB large.
In Breadboard mode is very easy to trace the wires. One nice feature is that the simple click-and-drag on a net adds a bendpoint and bends the trace.
The library is real funny structured, you can choose between CORE parts – which includes the Mystery Part (3 pins, 100mil, inline), MINE (yours), ARDUINO – 12 parts, PARALLAX – 9 parts – Basic Stamps and Propeller, PICAXE, Sparkfun, Snootlab and CONTRIB.
Changing component values is easy, select from a drop-down menu.
Importing a new component is limited to the proprietary *.fzpz format.
The autorouting is also nice and you can easily correct by click-and-drag.
Design Rule Check seem to work ok, it founds some intentional errors.
The export menu offers: image export(pdf, jpeg, svg, png and ps), production export(etchable normal and mirrored pdf or svg and a extended gerber option) and the standard BOM & XML Netlist.