Mr. Stoneship just posted his del.icio.us link to Inform 7, the interactive fiction development language. I don't know how such a cool program could so quietly creep up on us. It's a very interesting approach at a GUI with an English-like programming language and lots of new ideas:
There are several views on your game, with a transcript view that can perform something akin to unit tests on your game output, the game is written pretty much as english text, you have a tree view and transcript of actions that can be re-run, and you can switch between a running game and a game being designed and do something like "fix and continue".
The only trouble is, it doesn't just have the same name, but also the same file extension as the Inform drawing program... I sent out messages to the authors, hopefully they'll work something out.