A few days ago some Marble Blast DLC was released.

The "Marble Fu" pack is 200 pts and it includes 5 new multiplayer map and 1 new achievement.

I must say, I bought this pack and its great. 200 pts is a great deal.

Also there is another map called "Marble it up!" for free and it also has an achievement with it.

From the achievement list it looks like there is another map pack coming out but I don't know when.