FPSConsole

FPSConsole is an open-source command prompt replacement for Windows 2000/XP operating systems. Here is a list of some supported features:

Semi-Transparent Window
Has the same kind of hide/show system like they have in those first-person shooters (+other games).
Extendable (Almost any language can be used to extend FPSConsole).
Configurable (The aim is that the user could change anything s/he wishes, but still it should work with (almost) zero configuration.).
Built-In Lua Interpreter (See the links section.).
Can be used to execute all commands that the normal Windows command prompt supports.

And here is a list of some features that I'm planning on:

The possibility to use background images.
Support for other operating systems.
Full piped input support for extensions (currently full output support is implemented but input still requires the use of Dynamic Data Exchange.).
And about million other things...

You can also find some screenshots from the downloads section.