Transformational geometry software I'm doing a third year Geometry course involving transformations and isometries of the Euclidean plane. We're learning about the four isometries - rotation, reflection, translation and glide-reflection.
Is there any (free, preferably open source) software out there that can help me visualize these sorts of problems?

One could be Cinderella. I used it in a limited manner in my class while working on Euclidean Geometry. However, it is free to try, At an affordable low price, a license will make it easy to provide all students and teachers with a legal copy of Cinderella that they may use in school and at home. 
