I live in Australia and while it is an awesome country, the USA has great deals available online that only ship to American addresses. Freight forwarding services provide a great option and have the added benefit of receiving and holding shipments while you are travelling.
The service I use is called MyUs.com. For a low annual fee they will provide you an address in the USA and hold parcels until you are ready to have them shipped to your home address.
This is a great service for travellers as you do not need to ensure someone is home to collect deliveries and if you are overseas allows you to collate packages and save on postage.
I used Visaprint and created some very cheap address labels to make it easier to post packages while travelling and can have items sent home after the trip.