From a US mainland location, Amazon is freaking fantastic.
I really really missed it while I was back in Oz.
Amazon stock all sorts of stuff not just books, as well as being a store front for all sorts of other businesses.
I buy all sorts of tools, hardware and gear on there.
The best part is, if they stock it, shipping is free for orders over $25 dollars. This makes it cheaper for a lot of stuff than buying locally or even from Ebay (shipping from HK).
We have had great success with Amazon's second hand books too.
But postage to Oz would probably be killer.