Synonymful - Improve your vocabulary and communicate like a pro.
RegExr - RegExr.com is an online tool to learn, build, and test Regular Expressions.
Open Source Alternatives - 200+ open source alternatives to popular B2B tools
Expresso - 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 with an extensive knowledge of regular expressions.
Grammarly - Clear, effective, mistake-free writing everywhere you type.
rubular - A ruby based regular expression editor