This is a bit late, but I knew I was going to be away from home for the election (transitioning from NZ to AUS) so I requested an absentee ballot. However, in my rush to get things done before my big trip, I had failed to complete the ballot. No problem I thought, I'll just mail it from LAX while I wait for my plane to depart. Except, I forgot, and I was well on my way to New Zealand by the time I realized the ballot was still in my carry-on.
My solution: I mailed it from Auckland Airport as soon as I arrived. I found a shop near the arrivals area that sold stamps, and I bought an airmail stamp for it. The clerk said it should arrive in time for the November 7 deadline.
Some people back in the US would think I was taking a bit too much of my precious holiday time to finding a place to mail my ballot, but I thought the election was far too important to forfeit my vote. Especially since in far too many countries, people either can't vote, or the election is for "display purposes only."
Question for the Aussies: is it true that you are REQUIRED to vote, and if you don't you get fined? That's what my hotel clerk in Cairns told me.