From the back cover:
"Champions in 3-D is the dimension-travelling sourcebook for Champions. There are campaigning guidelines, play tips, and 31 parallel worlds - everything needed for a cross-dimensional scenario, or even campaign. Next time a hero's Extra-dimensional Movement backfires, just flip through this book, pick a dimension, and away you go!"
The longer, more detailed dimensions are Dreamzone (a world occupied by nightmarish boogeymen), Horror World (a world in which a group of sentient parasites took over the world), Fantasy World (a standard swords-and-sorcery setting), Nazi World (where the United States was taken over by an immortal Fourth Reich), and Backworld (where the classic Champions villains are heroic freedom fighters but never win, and the classic Champions heroes rule a bureaucratic dystopia and encourage kids to do drugs); these worlds include detailed backgrounds and multiple scenarios.
After that, there are several one-page "mini-dimensions", including Alien World, Anti-Mutant World, Aztec World, Camelot, Cartoon World, Confederate World, Dinosaur World, Disaster World, Egyptian World, Hero World, Japanese World, Mad Viking World, Magic World, Mecha World, Monster World, Normal World, Old Russian World, Old West World, Prehistory, Rome World, Soviet World, Techworld, Victorian World, Undersea World, and Wimp World.
There are also guidelines for creating new alternate earths, as well as a fairly detailed Random Dimension Generator