gnome-do

Inspired by QuickSilver for Mac OS X, Katapult is an application launcher for KDE 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.

GNOME Do (Do) is an intelligent launcher tool that makes performing common tasks on your computer simple and efficient. “GNOME Do” not only allows you to search for items in your desktop environment (e.g. applications, contacts, bookmarks, files, music), it also allows you to specify actions to perform on search results (e.g. run, open, email, chat, play).