If you haven't done so already, you should check out Light Table. It's a great new IDE that is trying to approach the way we go about programming in a different manner, kind of like what Bret Victor suggests.
Leaving the philosophical aspects aside, Light Table is also interesting from a technology perspective. First of all, its architecture allows for plugins to be "first class citizens", able to do anything within the IDE, as if their code was part of the editor's core. Second, LT is a packaged webapp. It's written in ClojureScript and packaged with node-webkit, so it's pushing both ClojureScript's development and the Web forward.
Recently, the code was open sourced and the plugin infrastructure was made available. It's been less than a month and the community has already added support for Ruby, Haskell, Markdown, LaTeX and more, in addition to the "standard" Clojure and Python.
Since the project was open sourced, I contributed with a few bug fixes and enhancements, and I even wrote my own plugin. I have to say, hacking on Light Table is pretty easy, thanks to the nicely written codebase and to the Behavior Object Tag architecture. As for plugins, there's a template that gets you up and running in no time.
So if you are looking for a new IDE to try, or a young open source project with a friendly community to contribute to, I suggest you take a look at Light Table!