You'll find plenty of keyboard-shortcut launchers floating around for Mac OS X, but Quicksilver's stylish interface, small footprint, and many customization options set it ahead of the pack. You activate this open-source program via a user-assignable hot key that spawns a small text field for entering abbreviations to locate applications, documents, or anything else.
Quicksilver offers multiple interface choices, from a menu bar to a transparent bezel that hovers over your desktop. Its other features include a task viewer, a "shelf" for storing frequently accessed files, and a clipboard history. The latest version of Quicksilver adds support for OS X's Quick Look features, letting you preview URLs and files using a key command straight from the Quicksilver interface. It also offers several fixes, updated plug-ins preferences sidebars and a new Extended Documentation window.
Quicksilver is a fantastic addition for anyone looking for alternative ways to launch applications from the Dock or to hunt through the Finder for files. This version requires Mac OS X 10.6 (Snow Leopard) or later.