I use EagleCad for designing the boards and an add in ulp called pcb-gcode to make gcode files.

You can download Eagle and use it as freeware for "small" boards" and hobby use and the add in is also freeware and can be found on the eagle site or through its yahoo group:
pcb-gcode : The pcb-gcode User's Group

Works great for those one off boards and if you want "autoleveling", there is a version that runs on an older version of eagle also.