The software listed on this page is FREE and Open-Source!
Slic3r is the tool you need to convert a 3D model into printing instructions for your 3D printer. It cuts the model into horizontal slices (layers), generates toolpaths to fill them and calculates the amount of material to be extruded. Visit slic3r.org to download.
Pronterface (part of the Printrun suite) is a machine control interface. It will allow you to manually control your printer and to initiate prints from your SD card.
Mac Download (choose Printrun-Mac-03Feb2015.zip)