It's pretty well known among gamers that the map to D&D's Mystara setting (née "The Known World") is based on the arrangement of Earth's continents in the late Jurassic period. I hope it's now equally well known that many seminal pulp fantasies take place either in the Earth's imaginary past or in a speculative future, at times when the continental outlines were different and (presumably) the laws of reality are too. I've always been fond of using real world maps and tweaking them in various ways to produce "fantasy" maps. This has the advantage of creating broadly believable geographies and it saves a lot of time to boot.
Lately, the players in my Dwimmermount campaign have begun to grow slightly curious about the world beyond the ancient Thulian mountain fortress and the area in its immediate vicinity. There's not much danger they'll start wandering very far afield, never mind exploring other continents, but I've begun to give some thought to the vague shape of the world. In doing so, I've been poking around with maps of possible supercontinents of Earth's far future -- millions of years from now after continental drift has changed the face of the planet.
Of those in the graphic above, I'm particularly fond of Pangaea Proxima, although I've also found images of an even later continent called Pangaea Ultima, which has a nice inland sea where the Indian Ocean used to be. I find these maps nicely evocative and, because they include places in the world I already know (albeit mashed up), it'd be easy for me to know "where to put the Vikings." That is, I could just pick a spot on the map, find out what it corresponds to in the real world and run with it rather than having to come up with things whole cloth. But now that you have, say, Africa butted right up against North America, you can get some cool interactions going on that you might not if you stuck with a map more closely mirroring Earth over the last few million years.