I started with pizza boxes, then went to the Iris brand boxes at the Container store. However, all I buy now (if I didn't have so many now
) are the ArtBin single or double boxes. I can get a small project in a single and a king size in the double. I always bought them on the 50% off plastic, everyday, or scrapbooking sales (one is coming this weekend) at Jo Anns. They cost more, but they stack well and have sturdier handles.