Synapse is a semantic launcher written in Vala that allows the user to easily launch applications as well as search for documents through searching Zeitgeist..
Docky is a Mac-like application dock/launcher for Linux that allows the placement of shortcuts on the dock.
The launcher built into the KDE Plasma desktop. While its basic function is to launch programs from a sort of mini-command-line, its functionality can be extended by "runner...
Plank is the default dock in elementary OS as well as a the underlying tech behind the Docky dock. Plank is a bare bones dock for those looking for something simple to launch app...
DockbarX is a stand alone dock that groups and launches applications.
GNOME Do is an app launcher that also allows searching online and offline.
Launchy is a cross platform app launcher that also launches documents, folders and web browser bookmarks.
Cairo-Dock is a Mac like dock for easily launching applications that is themeable and has a built in stand alone DE session.
Avant Window Navigator
Avant Window Navigator is a Mac like dock that launches applications.