Silvershell is a Python interactive interpreter with intellisense and lots of other features. It can run on the Windows desktop with WPF or in the browser with Silverlight:
There's an important new bugfix release. I put a lot of irritating flaws in the "intellisense" to rest, including a major issue with member completion that crept into 0.6.0 at the last minute. Had I known there was going to be such a response I think I would have tested it more thoroughly.
As promised all source code is in this release. Please notify me of remaining bugs, either via email, or via the issue tracker on Google Code. Patches are most welcome.