A rather stylish online Solar System Orrery.
It is written in Flash I’m afraid, so if you are on iOS you’ll just have to look at the screenshot and imagine the moving planets. Perhaps I will write an HTML5 version using D3.js when I get a chance…
If your tastes are more retro, check out orrery in the marvellous ZX Spectrum Astronomy, including the whole 24-line BASIC program!
It is a great reminder of what you can do with a low-resolution display and a few tens of lines of code. Here is another example showing different trajectories.