Hyperspace Structures: Exploring the Fourth Dimension: Explains the properties of the hypercube and hypertorus. Shows models and video clips. Includes information on how these images were created using software and mathematics.
Mark Newbold's Java Stuff: Java applets that show intersections, morphing, and stereoscopic renderings of four-dimensional polytopes and optical illusions.
Regular 4d Polytope Foldouts: Java applets to view the shapes by rotating them.
Uniform Polychora: Some images, and the naming scheme that the author has used to categorize over 8000 of these shapes with.
Uniform Polytopes in Four Dimensions: Tabulates the convex uniform (Platonic and Archimedean) polychora.