Ipelets
An ipelet is an extension of the extensible drawing editor ipe. The following are ipelets that I have written.
Check the FAQ if you need help, and email me if you have trouble or if you have a question that is not on there.
Visibility Polygon

Given a polygon and a point, computes every point in the polygon visible from the point.
Smallest Circle

Computes the smallest circle enclosing a set of points.