Scotland uses the single transferable vote system. Australia, which probably has the best known system, and one that applies nationally, to the Senate, as well as at the State level, has had quite a lot of experience with it. There may also be Belgium, but I don't want to mislead you. The two main systems are Australia and the Australian States, and Scotland, which only implemented it in the last election.
On April 9th, 2008. See this statement in context.