"As tasks at hand get bigger, the space available on your desk seems to become smaller. When your workload is outgrowing your desk, there are a few ways to expand usable space. Just look up, down or sideways and think out of the box."
Up? Apartment Therapy offers that: "There's no reason ceiling-mounted storage, traditionally used in a garage, can't be installed inside."
Down? Many options, including our Horizontal Freudian Slip: "Buy a ready-made desk caddy that mounts or hangs off the side of the desk, like this one from Utretcht, this inexpensive option from Bed, Bath & Beyond, or the Freudian Slip from Tom Bihn (meant as a briefcase insert, but works great as a desk caddy, pictured above)."