Coauthor
Tool for group collaboration, discussion, keeping track of notes/results of meetings, etc. Its primary goal is to ease multiauthor collaboration on unsolved problems in theoretical computer science, so e.g. you'll find LaTeX math support; hopefully it will have applications in other fields too. 
Virtual Glass
Lets glass blowers design and visualize glass cane, and to get a sense of what that cane will look like on a blown piece, all on your computer (without lifting a pipe!). The goal is to allow the exploration of cane designs, especially new cane designs, and settle on a nicelooking design before going through the effort of making it. 
Mathematical and Puzzle Fonts

Interlocked Polygons
Illustration of how to interlock polygons that fall apart exactly when a specified Boolean formula is satisfied, as described in a CCCG 2010 paper. 