Extend your dock with Overflow

While there are many full-featured launchers and dock alternatives available, Overflow by Stunt Software keeps it simple. The interface features several wells, into which you can drop an application, folder, volume and so on. Simply click the Overflow icon in the dock to activate it (or better yet, let Quicksilver do the job), then click the icon representing what you're after. Simple and effective.

Overflow requires Mac OS 10.3.9 or later and costs $14.95US (or, if you're very quick, $9.95US at Maczot for the next couple of hours).