I recently found out the pile of boxes I've accumulated from countless online purchases I've made over the years can be put to good use through a donation site called Give Back Box.
Give Back Box's mission: The purpose of Give Back Box® is to provide an effortless and convenient method of donating your used household items. Give Back Box not only provides an easy way to be part of a truly good cause, it gives a secondary use to corrugated boxes and guarantees they will be recycled.. So this is an all-round CSR & Sustainability solution that costs you literally nothing.
The process is extremely easy. From the Give Back Box webpage, click the link to print out a UPS packing slip. Affix the packing slip to the box you'll use to return clothing, shoes or handbags.
My first donation - 3 year old backpack from eBags. I'll receive a $25 credit toward a future purchase. I've posted a screenshot of the other participating merchants.
Box hoarder no more.