Microsoft has added Double Fine Happy Action Theater and Rhythm Party to the Xbox Live Marketplace, along with a few other goodies as well.
First up is Double Fine Happy Action Theater for Kinect, which allows for up to five players ages 2 to 102 to participate in 18 various, mini-fun-time shenanigans It will run you 800 MSP, but there is also a demo available if you wish to try it first.
Rhythm Party is also new to the marketplace, brought to you by the find folks which created Dance Masters. The available exclusively for Kinect, the rhythm-action game allows you to be both the choreographer and the dancer. It will run you 800 MSP and there is a demo available as well.
Avatar Onslaught 2 is available now as well for 80 MSP in the indie games section. In it, your avatar is being attacked by a “massive onslaught of evil avatars” which you can take on solo, or with a friend via online co-op. The game contains global scoreboards and has a demo available for a trial.
Be sure and check the XBLM for availability in your area.