regular expressions 101 - Extensive regex tester and debugger with highlighting for PHP, PCRE, Python and JavaScript.
RegEx Lab - RegEx Lab allows you to test regular expressions.
RegexBuddy - RegexBuddy is your perfect companion for working with regular expressions.
Multi String Replacer - Replace multiple strings at once!
The Regulator - The Regulator is an advanced Regular expressions testing tool, featuring syntax highlighting and...
dnGREP - dnGrep allows you to search across files with easy-to-read results.