Erik Benson recently relaunched All Consuming with an emphasis on registered users, more media types (movies, music, etc., not just books) and … support for free-form tagging of those things. A folksonomy for books! I like it.
It’s a little sparsely populated yet, but I can’t wait for this thing to grow and seeing some tools emerge for slicing and dicing of tags (intersect:Cooking+Physics ?).