Take a look at Cubify Sculpt: Cubify Collections - Cubify Sculpt 3D design software 3D Systems felt the need to offer an inexpensive program for STL mesh creation and modification to go with their new line of consumer-level 3D printers; the result is Cubify Sculpt. It's a good complement to Cubify Desgn, which deals with more mechanical types of parts - Sculpt is for more organic ones. Sculpt is based on Claytools, a much more expensive program that works with the Sensable (now Geomagic Sensable) force-feedback arm device. It imports STL files and allows them to be modified in various ways; then it will export the results. There's a free download available that you can try out.
Andrew Werby
www.computersculpture.com