Codenode, a project allowing you to interactively write and run code from any web browser (a project I started with one other dev a while back), has been seeing a lot of great progress by a longtime contributor.
I personally have not been able to work much on Codenode in recent months, but an amazing contributor I've never personally met, James Casbon (http://twitter.com/casualbon) has been doing some great stuff with it.
Specifically, he just set up an online example of Codenode here: http://live.codenode.org and is asking for feedback.
Edit: An example of plotting is here: http://codenode.posterous.com/livecodenodeorg-is-back