Keypirinha - A lightning fast and flexible keystroke launcher for Windows. No installation required (portable).
i3 - A dynamic tiling window manager designed for X11, inspired by wmii, and written in C.
Synapse - Synapse is a semantic launcher written in Vala that you can use to start applications as well as find and access relevant documents and files by making use of the Zeitgeist engine.
dwm - dwm is a dynamic window manager for X. It manages windows in tiled, monocle and floating layouts. All of the layouts can be applied dynamically, optimising the environment for the application in use and the task performed.
DockbarX - DockbarX is a standalone dock that groups and launches applications.
Openbox - Openbox is a highly configurable, next generation window manager with extensive standards support.