In the early days of Michael's obsession with planets, I was discussing orreries with my friend Matt K - also quite a star-struck young man. It would be lovely to have a beautifully precision engineered $30,000 orrery, with all the planets spinning on their axes as they swoop around a sun about the size of a beachball. I can just see it in one corner of our living room - the orrery corner. No touching now! Only dad is allowed to give it a light dusting, once a (Mercurial) year.
Anyway. Back in the real world, Matt suggested that there are some great computer simulations available online. Huh, I thought. You get what you pay for - there'll be freeware available where the planets are chunky dodecahedrons that actually bump into each other occasionally due to a glitch in the Lingo coding, or the floating point something-or-other.
I was dead wrong. This is freeware, it is fantastic, and I urge you to download and start playing with it immediately!!! (12.4MB download.) Here are some short screen-capture animations and a couple of stills. It is deeply interactive - you can set it going at any speed you wish (second=second, second=day, second = month and graduations thereof) and then alter the point of view at will.
So thank you to Matt K, and thank you to SSSim. I think they are based in Japan, but their site is extremely reticent to name names or take credit for this amazing achievement.