I found the link in a post on Neil Gaiman's blog. I've only browsed a few of the character entries so far but it's a cut above the usual fan shrine. The entries I read do recap what is known from canon but they also include outside material such as the origin of certain characters in folklore and the meanings of the angel's names.
Each entry I've looked at is illustrated with excellent fan art. some of it captures my vision of the characters, some doesn't, but it's all very well done. I'm going to be reading through this one a few entries at a time until I read it all.
This is an invaluable resource for someone who is writing a paper or fanfic based on the book. For the rest of us it's a fun read.