Interesting Facebook Pages and Groups

Every time you log on to Facebook, there is a good chance that you will find a message from someone asking you to join a page or a group, and become a fan of their favourite food, celebrity, charity, or music icon.

Most of these end up just being a waste of time, but every now and then a real Gem turns up, whether because it is useful, funny, or entertaining in some way (for example the new Michael Jackson Facts page)

What are the most interesting pages or groups that you've come across and that are music related? Feel free to mention those that are not related to music too if they're really really interesting :D