dnGREP - dnGrep allows you to search across files with easy-to-read results.
DocFetcher - DocFetcher is a portable German/English open source desktop search application.
AstroGrep - AstroGrep is A Microsoft Windows GUI File Searching (grep) utility.
Everything by Voidtools - Everything. Locate files and folders by name instantly. Everything. Small installation file. Clean and simple user interface.
PowerGREP - Quickly search through large numbers of files on your PC or network using powerful text patterns to find exactly the information you want. Search and replace with plain text or regular expressions to maintain web sites, source code, reports, ...
Agent Ransack - Agent Ransack is a tool for finding files and information on your hard drive fast and efficiently.