I would not want to have to do without my Moleskines. These are the legendary pocket-size notebooks used by artists and thinkers for the past two centuries--from Van Gogh and Picasso to Ernest Hemingway and Bruce Chatwin, from Charles Spurgeon and John Ruskin to Hilaire Belloc and John Buchan.
I’ve taken them all over the world and rarely am I without one (or two). I use the lined journal as well as the daily diary. I keep a few with watercolor-specific paper for sketching and drawing. And I've just discovered the new Moleskine City Guide Series (a combination journal and map book for cities like London, Vienna, and Prague).
I have stacks of old Moleskines--filled with random notes, outlines, lists, reviews, goals, agendas, piorities, quotes, squibbed ideas, and journal entries. And I always keep a few extras on hand--just in case. Nothing's better: