FreePCB is a free, open-source printed circuit board layout editor for Microsoft Windows, released under the GNU General Public License. It is not quite finished, lacking some important features such as a Footprint Editor, Design Rule Check and Autorouter. However, it is quite capable of laying out a PCB and producing Gerber files. Some of its features are:

- 1 to 8 copper layers
- Board size up to 60 inches by 60 inches
- Footprint libraries courtesy of Ivex Design International Inc.
- Copper fill areas
- Imports PADS-PCB netlists
- Exports extended Gerber files (RS274X) and Excellon drill files

If you use FreePCB to design a PCB, I would STRONGLY suggest that you check your Gerber files with a program such as ViewMate (available for free here) before spending any money to have the boards manufactured.