-- I AM PROBABLY NOT GOING TO CONTINUE DEVELOPING KATAPULT --
I began developing Katapult primarily for two reasons: the first is that I find using Alt+F2 to open anything other than programs unpleasant, and that only works well if the program you're opening is a simple command in your path. The second is that KDE currently does not have any convenient way of searching for particular items (e-mails, etc).
However, it seems that our wonderful KDE developers are taking care of that. KDE 4 is supposed to include a new contextual search engine, which will be more powerful and better integrated than anything I have the ability to produce. I may make an attempt to contribute to this project, or I may try making a Quicksilver-like interface to KDE 4's engine after its release. I hope to soon contribute something new to KDE and the open source community in general.
Katapult is an application for KDE, written in C++, designed to allow faster access to applications, bookmarks, and other items. It is plugin-based, so it can launch anything that is has a plugin for. Its display is driven by plugins as well, so its appearance is completely customizable. It was inspired by Quicksilver for OS X.