I stumbled upon the It's Not All Mary Poppins blog today, and the Book Binge Challenge. The way it works is simple - you just keep track of every book you read for the month of May (ok, I do that anyway). At the end of the month, everyone involved will blog their list of books (easy enough). You can included re-reads, books you start but don't finish (just note where you stopped), read-alouds (125 pages or more), and textbooks (at least 100 pages long). To participate, you can sign up here.
Oh, and it's officially starting Monday, May 5, but you can sign up throughout the month of May.