Radi – A Visual Design App For Web (Mac-Only)
It has built-in tools for creating/editing graphics (they can be imported too) and generating animations with
<canvas> output that work in all modern browsers including mobile.
There are ready-to-use filters + effects and you can always add your own code to create more customized stuff.
The application is also pretty powerful in rendering video. It can even -very quickly- convert a web animation into a HTML5 video.
Radi has a very short learning curve as it is like a mixture of well-known image editing and animation tools but with the friendliness of web technologies.