3 links
Mark Newbold's Java Stuff
dogfeathers.com
Java applets that show intersections, morphing, and stereoscopic renderings of four-dimensional polytopes and optical illusions.
Uniform Polychora
members.aol.com
Some images, and the naming scheme that the author has used to categorize over 8000 of these shapes with.
Uniform Polytopes in Four Dimensions
members.aol.com
Tabulates the convex uniform (Platonic and Archimedean) polychora.