regexxer - regexxer is a nifty GUI search/replace tool featuring Perl-style regular expressions.
dnGREP - dnGrep allows you to search across files with easy-to-read results.
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, ...
AstroGrep - AstroGrep is A Microsoft Windows GUI File Searching (grep) utility.
Agent Ransack - Agent Ransack is a tool for finding files and information on your hard drive fast and efficiently.
Search & Replace Master - Search & replace the text in your files in seconds.