Everything by Voidtools - Everything. Locate files and folders by name instantly. Everything. Small installation file. Clean and simple user interface.
Keypirinha - A lightning fast and flexible keystroke launcher for Windows. No installation required (portable).
DocFetcher - DocFetcher is a portable German/English open source desktop search application.
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.
X1 Search - X1's Lightning-Fast Search Software. Premium Alternative to Windows Desktop and Outlook Search.
DockbarX - DockbarX is a standalone dock that groups and launches applications.