GoodReads

With 62 million books currently in their library database, this is a site to visit if you can't actually afford a book. This'll keep you busy reading until you can. And if you're already a reader, you'll be stunned by the sheer volume of material here and the range of activities available.

The concept is simple: sign up (it's free) then fill a few virtual shelves with books you've read, or are reading, or want to read, or categorize them in other ways you find appropriate (my favorite just now has to be "overrated drivel"). The busy librarians will add any new books you've discovered to their ever-expanding lists, and you're free to review your books and read some of the other members' reviews too - sometimes there are literally thousands of reviews for just one book. Whew. If you've got a whole library at home, you can go right ahead and add the lot. But even if you've only got "Bill Gates: The Road Ahead" there's a niche for you too. Maybe not such a big one.

Obviously if books aren't your thing, and sadly it seems that less people read books as time goes by, then you might still find yourself drawn in by other peoples' reviews and inspired to go read a book yourself and see what the experience does for you. Even for non-members, the amount of data here is astonishing; one book I picked at random had been rated more than 65,000 times and had more than 4000 reviews.

There is the now-obligatory social networking element too, of course, with interest groups and the opportunity to see what your friends are reading and recommending and have them peer over your shoulder as well. It's a pleasant enough break from YouTube, viral videos, and the more popular visual entertainments that web 2.0 has to offer. You might even be tempted to grab a book and actually go offline for a while. Scary, huh?