Slic3r 1.3 for Mac can be downloaded from our website for free. The actual developer of this free Mac application is Alessandro Ranellucci. Slic3r for Mac lies within Design & Photo Tools, more precisely Viewers & Editors.
From the developer:
Slic3r is the tool you need to convert a digital 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.
Slic3r is bundled with the most important host software packages: Pronterface, Repetier-Host, ReplicatorG and has been supported/funded by almost all the main 3D printing companies in the world.
You may want to check out more Mac applications, such as PrusaControl, which might be similar to Slic3r.