Last week I used a gift card and bought the dvd version of Neil Gaiman's Neverwhere. It's a limited 3-hour long series done for the BBC. Dave McKean, who did artwork from time to time for Sandman, did the animation for the title sequences and Brian Eno did the musical score. It's not hard to imagine all three sitting down for tea and dicussing odd things like Tibetan mythology and patterns of music created by the human body.
Being the BBC, the production quality of the series is a little different than what U.S. audiences are used to. The action fights are a little sloppy, and special effects and sets are not quite up to the level of even a Sci-Fi channel show. But the acting is decent, and it's a great storyline. A very different experience than the novel, especially since it's broken up into six seperate episodes. The DVD also includes commentary from Gaiman, which I haven't watched yet. But it's at least worth a rental if you like fantasy-oriented stories, and probably worth buying if you're a big fan of Gaiman.
After looking up some info on the project, I was surprised to find out the novel came after the series. According to what little I can find, Gaiman wrote the novelization while the series was being filmed. I don't know if that was just his way of bringing the story to a U.S. audience, if he was not happy with the turn-out of the project, or something else entirely.
Gaiman and McKean have a film hitting theatres this year called Mirrormask that looks promising. I've also heard some recent rumors that they're working on a version of the Beowolf myth, one of my age-old favorite stories.