My Booktown Bible has come in really handy when I need to remember what color eyes Mr. Everett has or the name of Tricia's attorney (who hasn't shown up since the first book--but needed to be mentioned in the fourth book).
I'm currently working on my Victoria Square Bible. It consists of a list of characters, their traits and a description (however brief) of what they look like, a list of businesses, facts about the little town of Jones Mill (which may or may not be changed by the final draft--I'm leaning toward changing it. One caveat: it's got to have "Mill" as the second word -- but I'm open to ANY suggestion), etc.
Besides being a vital aid to writing the subsequent books, creating this bible is a great way to actually keep from writing.
What are you doing to keep from working on your work-in-progress?