Its rare that I come across applications that I haven't used, andeven more rare is that I find them interesting. I found two today. Katapult is something I must try out. I've been looking for something like this for a while. Even more surprising is they are KDE apps. How did I not know about these!
1) Katapult Unlike Yakuake, the other time saving application in my list, this app comes pre-installed with Kubuntu. There really isn’t much to it, aside from not ever having to use menus to find your applications… just alt-shift and start typing the name, it will fill it in for you (think Quicksilver, for you Mac users). You can open programs, files, use a calculator, etc. By far my favorite part of kubuntu, and one not easily replicated by any program under the GNOME desktop.