Here is an improved method of generating Double Sided PCBs that yields just about perfect results first time. You will need Eagle to define the PCB artwork and generate the Gerber Files (that can be used to produce commercial versions of the PCB), FlatCAM to generate the CNC files and AutoLeveller to create a flat virtual surface that makes sure you can get very high resolution tracks and isolation. Part 1 covers the above process and modelling and Part 2 covers cover the actual machining of the PCB.