Just use milk crates (not the ones you buy at wal mart but the actual 4 gallon milk crates). Tie together with zip ties and if you wish you can spray paint or wrap in fabric for decoration. The fabric bins fit perfectly in them.
Play room-DIY seat covers for plastic crates- great idea for a reading center (esp. in a small classroom). Just store books/materials inside the crate, and kids have a seat as they read their books and complete their work!