We've just created a Playground for testing out Javascript and the Canvas tag with Raphaël and EaselJS... At the moment, we're still loading example code to use with the playground, however there is also a default "blank" sandbox that you can use to test your own code in provided as well.
The feature set will grow over time, including contributing your own examples; however for now feel free to have a play and leave a comment here with any suggestions for features or code samples you may like to share.
Enjoy!