For boxes, in the past I've had luck with liquor or wine stores. Call them up or show up and ask if you can take any boxes. They usually give them to me for free and are very sturdy.
Since it's already Christmas shopping season, lots of big box retailers (electronic stores, hardware stores, etc.) probably have had a lot of new products come in, so they might have boxes too.
The dumpsters of businesses that have lots of incoming merchandise provide free boxes. Try Walmart, for example.