A downloadable stick figure animation program. Very few options for what to animate (think MS Paint), but what it lacks in cute icons and backgrounds it makes up for in granular control and sophistication of the animation.
100% free and available for Windows, Mac, and Linux.
Pencil2D – opensource animation software
Pencil2D is an animation software for both bitmap and vector graphics. It is free, multi-platform, and open source.
A web-based tool for creating animated videos, very similar to GoAnimate in options and user-interface. PowToon markets itself as more of a business tool and its styles are less cartoon-like than other tools. With the free account, users are able to save videos up to 5 minutes long and can upload a voice-over track and/or audio track.
Caveat: The free version does not allow you to download your video as a file. All free videos bear the PowToon logo.
Open source software for producing a 2D animation.