SURFEX - Visualization of Real Algebraic Surfaces. surfex (with S. Holzer, a tool which is quite easy to use, with many features (sevearl surfaces, curves on surfaces, ...), it uses surf (see below)), surfer (with H. Meyer, C. Stussak and others, very easy to use, and easy to install under Windows/Linux), but much fewer features than surfex, it also uses surf (see below)).