NonEuclid

NonEuclid is Java Software for
Interactively Creating Ruler and Compass Constructions in both the
Poincaré Disk and the Upper Half-Plane Models of Hyperbolic Geometry
for use in High School and Undergraduate Education.

Hyperbolic Geometry is a geometry of Einstein's General Theory of Relativity and Curved Hyperspace.

NonEuclid has moved. The new location is:
http://cs.unm.edu/~joel/NonEuclid/