A Small Addendum
I just realised that Susanna Clarke's http://www.jonathanstrange.com/ website is now up and running, which I should have discovered before putting up all those links in the previous post. It's only just up, but it has some fun things up already, including a short story called "The Duke of Wellington Misplaces His Horse", which is, in its way, a Stardust-Jonathan Strange & Mr Norrell crossover story, which Susanna originally wrote for the Fall of Stardust chapbook.