Belgian 3D Printing service i.materialise researched the popularity of 3D design applications for 3D printing. They based their ranking on multiple factors, including community activity, youtube and more. Blender came out on top!
We did a research on the most popular 3D modeling software for 3D printing and found out that Blender has the biggest, most active community. Blender even beats SketchUp, Solidworks, and the Autodesk Family. You can find the entire report here: http://i.materialise.com/blog/top-25-most-popular-3d-modeling-design-software-for-3d-printing