Adobe Flash Alternative: Synfig Studio

Synfig Studio is a vector based 2D animation program. It is designed to produce feature-film quality animations, though it can also be used to create great vector images. Synfig Studio has an alternative to manual tweening, which prevents the need to hand draw each frame. Synfig Studio features many professional features like spatial and temporal resolution independence (sharp and smooth at any resolution or framerate), high dynamic range images, and a flexible plugin system.