You can start buying downloadable content for New Super Mario Bros. 2 this Thursday.
The first three DLC packs for the game, each including three courses, are the Gold Rush Pack, Coin Challenge Pack A, and Nerve-Wrack Pack. Here's Nintendo's description of each:
Gold Rush Pack: Fun new courses that give novice players the best chance to collect lots of gold, and veterans the chance to set even higher Coin Rush records.
Coin Challenge Pack A: The New Super Mario Bros. 2 website will track the rankings based on the scores for this pack, enabling players to measure their scores against other tallies from around the world in these more open courses.
Nerve-Wrack Pack: Intense new courses designed for veteran players looking for new challenges.
DLC for New Super Mario Bros. 2 was first detailed in Japan late last week. Nintendo says they plan to release more DLC packs later this year; the second will arrive at the end of October and the third will hit at the end of November.