DocFetcher - DocFetcher is a portable German/English open source desktop search application.
dtsearch - dtSearch - The Smart Choice for Text Retrieval since 1991.
Agent Ransack - Agent Ransack is a tool for finding files and information on your hard drive fast and efficiently.
Lemur Project - The Lemur Project develops search engines, browser toolbars, text analysis tools, and data resources that support research and development of information retrieval and text mining software. The project is best known for its Indri search engine.
SearchMyFiles - Alternative to the standard Search For Files And Folders module of Windows. Duplicates search is also supported.
Everything by Voidtools - Everything. Locate files and folders by name instantly. Everything. Small installation file. Clean and simple user interface.