Namely is possibly the fastest way to open applications. And unlike some other launchers, it doesn't require any learning.

You simply activate it using your preferred keyboard shortcut, start typing part of an application's name and see a list of matches as you type. Most of the time, one or two letters are enough. In fact, Namely learns your habits and makes your most-used apps even quicker to access over time. It's basically Spotlight for applications, only much faster, and highly addictive.

Requirements:
OS X 10.5 - 10.6
Universal Binary

Also available is:
Universal Binary version 2.1 for OS X 10.3.9 through 10.4