This site answers the age old question: “How Does One Obtain the Ability to ‘See’ in Four Spatial Dimensions?”
Also in the do it yourself category, make your own posters with the Rasterbator: “Welcome to the Rasterbator – NOW IN COLOR!The Rasterbator is a web service which creates huge rasterized pictures out of relatively small image files.”
Finally an interesting application of an impressive 3D visualization tool: base26 shows a map of 4 letter words that you can navigate, sorted at the top of the graph by the first letter of the word. Why are words starting with “K” so different in distribution that those starting with “O”? If you have any explanations I would love to know.