If you've never heard of The Sketchbook Project before you can read more about it here. It's a project open to everyone, not just artists. You pay a small fee for your sketchbook and choose a theme that you would like to work with from the long list thats on the website. When you receive your sketchbook you will see that it has a unique barcode printed on the back, as well as your name, location, and chosen theme. The barcode makes it possible for the library to notify you every time somebody takes a look at your sketchbook!
I think it's a great initiative. It gives you the excuse to experiment and do your own thing for a while. It's also a really good way of getting your work out there for other people to see.
Below are some photos I took of my sketchbook the night before I sent it off. I gave myself a lot of freedom with this project, and didn't worry about whether it was the best work I'd done or not. I just had a lot of fun with it, and ended up with something a bit crazy and unexpected. But hey, that's what sketchbooks are for in my opinion.