Silicon Valley Dictionary - Urban dictionary meets Silicon Valley

Grammarly - Clear, effective, mistake-free writing everywhere you type.

Urban Dictionary Random Word - Random word when you open a new tab in Chrome

LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.

Words For That - the reverse-Urban Dictionary of the internet

Editsaurus - Highlights potential pitfalls in your writing to encourage good habits.