Waterstones have got a three for two offer on Moleskines at the moment, I bought a large sketchbook and a 2008 diary and got another large sketch, for nearly free. (The lower priced item is the free one).
They cost a lot more than I would normally pay for a drawing book but having used smaller Moleskines to doodle in I am converted. I love using dip pen and ink in them and the 13 x 21cm size is just perfect, not too big and not too small. With luck I am going to use them on the 'big project' that will be starting soon.