Mighty Box is a still under development, open source application launcher for Windows which is touted as the Windows version of Mac’s QuickSilver software. With this application, you can control your Windows machine using just the keyboard, launching apps, manipulating files and data, running scripts, sending email, and more. What’s even more amazing is that not only does Mighty Box let you do these sorts of things, it could potentially let you do them without opening the relevant program. (For example, you could send an email without starting your email program).
The software is still in early alpha stages, so expect some bugs if you try it, but it’s available for download here.
Also note that the developer stopped work on this app some time ago. However, the code is open source. That means anyone could pick it up where he left off. (Could someone please do so? This would be so cool!)