It would be nice if U.S. payphones were as cheap to call across town as Singapore payphones are to call halfway across the world. A recent bar graph in The Economist indicated that SG had the second-cheapest long-distance rates in the world, and whoever #1 was wasn't much cheaper.

You can buy phonecards in 7-Elevens, which are everywhere. They come in a variety of dollar amounts but I've always bought SingTel SGD 10 cards. That bought me three longish phone calls to the US on SingTel (001 + country + number) with money to spare. I think other carriers are even cheaper; they advertise all over the place, especially 008.