DocFetcher - DocFetcher is a portable German/English open source desktop search application.
rubular - A ruby based regular expression editor
Everything by Voidtools - Everything. Locate files and folders by name instantly. Everything. Small installation file. Clean and simple user interface.
RegEx Generator - RegEx Generator is a simple-to-use application that comes with the brilliance of intuitive regex and is also helping you out to test the regex.
Recoll - Recoll is a desktop full-text search tool. Recoll finds keywords inside documents as well as file names.
RegExr - RegExr.com is an online tool to learn, build, and test Regular Expressions.