STL Editor

From Floating Point Solutions:

STL Editor is a Stereolithography (.STL) file viewing, editing and printing application. The .STL file format has become the Rapid Prototyping industry's standard data transmission format and is the format required to interact with stereolithography machines. How often have you received a STL file from someone only to find that it contains errors or it is just not the way you wished it was? How often have you sent back a STL file for modification or scrapped it totally because you found it unacceptable? If this happens often then STL Editor is exactly what you need.