Smaller baskets can hold computer CD's, school receipts, or desk supplies. Medium baskets can hold papers to grade, Playstation controls, or computer cords. The larger baskets can hold newspapers, library books, or toys.
They can be found at thrift shops, garage sales, and clearance tables. Don't spend too much money on them.
For more on organizing, you can download the recorded webinar Organizing Your Classroom 101 for free at Homeschool Connections. Click on the link that says Recorded Events.