I confess to playing around with Facebook at work (strictly as a learning experience, of course!) and really like the Virtual Bookshelf feature I found on a colleague’s page. It lets you build a personal library with links through to Amazon, but it has a separate shelf for books you have read, are reading or would like to read. Tried it just for fun, and now when someone recommends a book and I like the sound of it I pop it on my bookshelf as a reminder.
It works better than the scrap of paper at the bottom of my bag, and it’s quite gratifying to move a book from ‘am reading’ to ‘have read’ shelf! Take a look at how it works if you like.