Listary - Listary is a revolutionary search utility for Windows
dnGREP - dnGrep allows you to search across files with easy-to-read results.
Keypirinha - A lightning fast and flexible keystroke launcher for Windows. No installation required (portable).
AstroGrep - AstroGrep is A Microsoft Windows GUI File Searching (grep) utility.
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.
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, ...