Paul Koning wrote:
http://www.geda.seul.org/ (EDA suite, including schematic capture,
Gerber viewer, circuit sim, etc.)
Be careful with the 'free' gerber viewers... I've been burned by them.
(I ended up with a solid power and ground plane due to a stray polygon
and it didn't show in the 'free' viewer)
I always double check with a commercial one now... (I still use the free
ones, but I always double check)
-brad