I recently spotted a neat-looking widget on a few friends' blogs: it displayed books they've read, with links to their rating and reviews of each book. I followed the links to Good Reads and signed myself up! It's a pretty neat site, and I've added a lot of the books I've read over the last few years, plus all the books on my to-do list. I haven't added any reviews yet, but I will. As it turns out, it's also a facebook app, so I added that as well, and deleted my old bookshelf app because it wasn't at all user-friendly.
So I think all my librophile friends and family out there should join too. You can get these pretty widgets in your blog! So fun.