Flipnote Studio is a free stop-animation drawing app that is only available on the DSi model of the DS. There's a new version of the application coming out for the 3DS, but you will have to manually transfer your animations over if you want to keep them.
Flipnote Studio 3D is coming to the 3DS for free this summer. The animations for Flipnote Studio are currently housed online, but those servers will shut down on May 31. If you want to grab your old animations before they disappear forever, you can head here for directions on what to do.
When Flipnote Studio 3D releases this summer, it will include more options than the previous version of the software. You will have access to more colors and layers, and you will be able to export your animations as GIFs for posting online.
[Source: Siliconera]