AstroGrep is a Windows grep utility that supports regular expressions, context lines, and advanced search options.

DocFetcher is an open source desktop search application that runs on Microsoft Windows, Mac OS X and Linux.

PowerGREP is a powerful Windows grep tool for searching through files and folder, performing complex search and replace operations.

dnGrep allows you to search across files with easy-to-read results.

grep is a command-line utility for searching plain-text data sets for lines that match a regular expression.