The Webwide World is an "earth-like" planet that runs interactively in Web-browsers. You explore it by rotating around it and zooming in with your mouse.
I think it's beautiful.
I recommend running it from a PC instead of a Mac - most Macs have lousy support for Java. The planet has recursive real-estate - many islands have littler islands around them, and so on. I suspect it's got many more islands all together than the number of people in the world, so there's plenty of room for everyone.
Technogeeky Info: The surface texture is formed by a summation of `perlin-noise' functions. Portions of this summation are used in various ways to form clouds, ocean, mountains, snow, etc. The starfield that surrounds the planet is also formed out of noise functions. The planet has atmospheric haze (how else could you breathe?).
More Technogeeky Info: Java really can't compute the planet in real-time. So I've got a new, patent-pending (yes, really) progressive rendering scheme, which renders the image as a gradually finer fractal pattern. It's "optimal" in the sense that no surface point is ever computed twice, and it provides a cool impressionist look while the planet is rendering (while actually only plotting squares).
Practically, what this gives you is a good sense of what the planet looks like well within the first second, even if you're running on a slow machine where the super-quality final rendering might take more than a minute.
Way Too Technogeeky Info: Normally, rendering would become intolerably slow as the user zooms in, since I need to sum ever more frequencies of noise with increasing magnification. But rendering doesn't get any slower, because I cache low frequencies of this summation into a grid of Catmull-Rom splines, so I only need to recompute the high frequencies. The code for the Java class I implemented to do this splining is accessable here.
I'm going to open it up for a real-estate grab at some point soon, thru a server-side registry. Anyone can have their own island, to own, build on, put messages on, set up shop in, or trade. I'm going to set up the rules so that "size doesn't matter" (apologies to SONY). Tiny islands with the right features (lakes, lagoons, proximity to the right cool places and folks, etc) will be worth more than big boring islands.
People can always find a really awesome tiny new island in the land grab (which can go on for quite a while) that had been overlooked. Then people can start to build their semi-automatically architected cities, trade messages, form alliances, etc.
I will also try by SIGGRAPH to finish the implementation of a "survival of the prettiest" (brilliant concept by Karl Sims - who is a living example) evolution scheme so that people can genetically evolve their own personal planet, which can appear mars-like, venus-like, or whatever. In this scheme, the user can ask that different portions of the planet have different "looks". They can click on the portion that they think looks best, which defines a median starting point for the next set of variations, and so on. Serve when done.
Under the hood, any particular "look" is actually a set of parameter values. But it will be more fun to let people evolve their own personal planet by example than to make people tweak some stupid sliders.