Does anybody know of a Windows Explorer extension that will add a pane giving an inline command prompt, set to the current directory?

I know that on Windows 7 I can Shift-Right Click and get Open Command Prompt here, but my desktop soon gets cluttered with windows when I do that.

The specific example that made me ask for this is my work with Mercurial: it would be great just to be able to go to my directory and type, in some pane in the window, "hg push", and see all my changes pushed up to the repository. But I can think of other uses as well, so I'm sure somebody must already have written this extension.