[obsolete: please don't mail me stuff at this address; I'm no longer there!]
Yes, you can mail stuff to me (or anyone else, for that matter) at the South Pole.
Address mail to:
David Cohn [or whomever]
South Pole Station, PSC 468
Box 400, APO AP 96598
Mail comes down on the C-17s, wedged between science cargo and vital supplies. As a result
Small is beautiful. Personal mail has lowest priority on the planes, and is stuffed in whenever it can fit. Multiple small things get through much better than one big thing, and those little Tyvek baggies have the best chance of making it through quickly.
Send stuff early. There's generally a big delivery push at Thanksgiving, and another just before Christmas. But sometimes nothing comes for a month.
Avoid stupidness in packing. Air New Zealand will freak out if goopy, sticky packages come their way. Mail is mostly shipped as DNF (do not freeze), but will first sit unrefrigerated on tarmac at CHCH and bake for a few days, then freeze on the unheated trip from the storage to the plane. Things that can go moldy (cookies?) are not recommended. Beth says fruitcake seems to survive just fine
Prohibited stuff: polystyrene packaging, anything that's alive (plants, seeds), hazardous and toxic substances
Discouraged stuff: aerosols, disposable batteries, non-reusable plastic containers, magazines and catalogs - stuff that will have to be hauled back out of Antarctica as trash
Packages have customs forms.
Some more information (but not tons) on mailing stuff can be found in the USAP Participant Guide