thankyou to "two roads" of eslcafe.com: "The U.S. post office has flat rate envelopes you can use to ship overseas. I think they're called "global priority flat rate envelopes" or something like that. They cost $6.50 for the smaller envelopes and $9.50 for the larger evelopes, and only take 4-6 days from the U.S. to Korea. You can put as much stuff in as will fit, no weight limit. The larger size envelopes are quite roomy, and it's surprising how much stuff you can cram in there. Except for a couple fragile items, I've had everything that I've had sent to me (including toiletries) sent by these envelopes, and it's always worked out great."
another update: ive been in korea for 10 months now. every couple of weeks, my pops sends me magazines and such in the mail, using the envelope pictured above, at $11 a pop.