I'm not much into the Harry Potter phenomenon, but I am in the middle of trying to learn WPF (Windows Presentation Foundation). I'm currently tackling WPF via Adam Nathan's "WPF Unleashed" book and plan to read the Petzold WPF book next (followed, perhaps, by the Sells/Griffiths book). WPF is conceptually very different from Winforms or other UI technologies that I've used, which makes the learning curve steeper than would be normal for "just another platform update". Anyway, you may be wondering what Harry Potter has to do with WPF...
Well, a month or two ago, the folks at Vertigo Software released a WPF reference sample application called Family.Show. The application is a genealogy tool that let's you manage a family tree, along with information and photos about the people in the tree. It's since been updated with more features and it's simply a great-looking application. If, like me, you're trying to learn WPF then the coolest part of Family.Show is that they've made the source available for download. Sweet.
Earlier today, Liam Molloy (of Vertigo) published a post about a family tree he created for the "Black family" from the Harry Potter series. Using Wikipedia, Liam was able to piece together a fairly large family tree for Sirius Black, including photos (of the actors/actresses from the films) and the background stories for many of the characters.
You can download Liam's data files for this family tree, load them up on your machine, and go to town with the info-browsing. Note Liam's warning at the bottom of his post -- while he made an effort to remove any spoilers for the just-released book, he says it's possible that there's still one or two in there. Not having read any of the books, I wouldn't know either way... I just think this was a very cool thing to do from a data visualization perspective.
So... whether you're into WPF or Harry Potter (or both?), you've got a reason to go check it out.
(Side Note: The only drawback I've found with the app Vertigo built for Microsoft is that the background whitepaper for it was published in the XPS file format... and even though I've got Office 2007 installed, I still had to download a separate "essentials pack" to view it. What's wrong with a simple PDF?)