Eagle, there's a free version with these limitations:
The following limitations apply to the EAGLE Light Edition in general:
* The useable board area is limited to 100 x 80 mm (4 x 3.2 inches).
* Only two signal layers can be used (Top and Bottom).
* The schematic editor can only create one sheet.
If you want more board space and are willing to pay, you can get a version with non-commercial lisence, or you can get the full version, which costs more.
It also has linux(which i use) and MacOsX versions.
http://cadsoft.de/