Essentially, the Classic Double Challenge will encourage you to read one older book (classic) and a newer book that relates to the older one in some way.
There are levels of participation, so you can choose how much or how little you'd like to commit to:
Small: You read 2 related books.
Medium: You read 4 books (2 sets of related books).
Large: You read 6 books (3 sets of related books).
Super Size: You read 8 books (4 sets of related books).
Sign up on this post any time from now until the end of 2012.
I'm committing to the small level, and plan on reading Jane Eyre by Charlotte Bronte (which I bought in England over a decade ago and haven't actually read) and Jane by April Lindner.