I feel the most effective marketing are continued improvement, word of mouth and of course positive reviews both in the App Store and in the press
Congratulations to FutureTap for this very special anniversary. Let's remember Ortwin Gentz purchased the location based app "Where to?" from tap tap tap one year ago. I suggest you have a read to the whole blog post. He mentions as a big mistake to change iTunes accounts and finds the effect of iTunes reviews more important than PCC and Adwords campaigns.
What I get from this experience is that FutureTap has used a rare but successful strategy to keep Where To? selling: Localization. I'm amazed seeing the difference there.