morehawes - 8:59 am on Sep 9, 2010 (gmt 0)
Hello and welcome to Webmaster World!
This might not be possible for you but I work alot with an ecommerce business who send out fairly high volume but don't buy any boxes (except a couple of 'pretty' ones for gift wrapped orders). Instead they recycle old boxes and scraps of cardboard and use a strapping machine to secure the packages. It's surprising what you can do with a couple of bits of cardboard and one of these machines. If necessary the package then gets brown papered or put inside one of those sealable bags.
There is of course the initial expense of the strapping machine but it has paid for itself time and time again. You can also use the fact that you recycle as part of your 'green' marketing whilst also saving you and local businesses the expense of getting rid of unwanted boxes (business rates even for recycling in the UK are not cheap!)