Penn State Online GIS Education and the Dutton e-Education Institute have put together a map that the user can reproject to 10 different projections. It is a site that would primarily be of interest to those who don’t have access to a GIS. Projections include Plate Carree (or geographic), Mercator, Transverse Mercator, Cylindrical Equal Area, Robinson, Lambert conformal Conic, Albers Equal Area Conic, Azimuthal Stereographic, Azimuthal Equidistant and Azimuthal Orthographic. The site allows users to specify the parameters of each projection, display distortion ellipses and plot and label a location on the map. The site makes use of ArcIMS to display the maps.

(Update: My apologies for failing to include the link!)