MassageTXT is described as 'Convert between text and structured data' and is an website in the Development category. There are more than 10 alternatives to MassageTXT, not only websites but also apps for a variety of platforms, including Windows, Mac, Self-Hosted solutions and iPhone. The best alternative is RegExr, which is both free and Open Source. Other great sites and apps similar to MassageTXT are regular expressions 101 (Free), Expresso (Free), RegexBuddy (Paid) and iHateRegex (Free, Open Source).
The award-winning Expresso editor is equally suitable as a teaching tool for the beginning user of regular expressions or as a full-featured development environment for the experienced programmer or web designer with an extensive knowledge of regular expressions.
Multi String Replacer is a small and portable application that can be used to replace multiple strings at once. Its main functionality is String Swapping in which can be easily and quickly done. String swapping consists on replacing WordX with WordY and WordY with WordX.
RegEx Lab allows you to test regular expressions. The app highlights and underlines text to show matches and capture groups. There's also a handy cheatsheet and a results list view. It has a replace feature too.