I use gEDA/PCB. The file formats are open and ASCII. The open file
formats make a wide variety of EDA automation tasks possible. The
ASCII format makes them easy.
I have switched from Eagle to gEDA/PCB. I have found gEDA to be a more
productive tool. The schematic capture is better but the PCB layout
seems more difficult. The scriptability is what has made the
difference. There are also tools for simulation.
Be careful of choosing a free version of an EDA tool that is crippled
or a tool that locks you in to a specific PCB vendor. There is a
learning curve associated with any EDA tool or other complex piece of
software. It will be very time consuming to switch tools.
The footprint library that I use is available at
http://www.luciani.org Also I have a variety of EDA automation scripts
on my site.
As an example of gEDA/PCB I did a remix of the Drawdio circuit design
that ladyada did (CC 3.0 BY-SA). The remix includes the EDA files and
documentation. All of the files are at
A couple of additions --
XCircuit http://opencircuitdesign.com/xcircuit is an open source
package that produces some very nice looking schematics. The
most extensive example would be the open textbook at http://www.ibiblio.org/kuphaldt/electricCircuits
If you use La/TeX you can create inline schematics using macros.
This could be useful for very simple schematics but I can see
this getting very cumbersome very quickly.