Dont expect a lifelike simulation of a 3D snowglobe and youll be happy with this app.
The snowflakes move fairly realistically (except for the initial scattering), but it all takes place on a 2D plane, so much of the fun in getting a real snowglobe to swirl its flakes like a blizzard is missing, but the app does let you put your own picture in the middle, and it tracks the orientation of the iPhone so you can make the flakes fall in any direction. Snowglobe also makes a nice demo for accelerator functionality.
Iritscen about Snowglobe