Synfig Studio - Just another WordPress site
Spine - Spine is 2D animation software designed specifically for software and game development.
CrazyTalk Animator - CrazyTalk Animator, the next level of 2D animation. Create actors using any photo or illustration.
Animation Paper - Animation Paper is a software package for doing 2D animation.
DigiCel FlipBook - Whether you do 2D, 3D or stop motion Animation, DigiCel FlipBook makes animation easier!
Animata - Animata is a highly advanced open source and real time animation program for the creation of animations and interactive background projections for concerts, games, films and much more.