Grammarly - Clear, effective, mistake-free writing everywhere you type.
Google Open Source - All of Googles open source projects under a single umbrella
Synonymful - Improve your vocabulary and communicate like a pro.
Opensource Builders - Find open-source alternatives to commercial apps
Analyze My Writing - Analyze My Writing is an online text content and readability analyzer.
LaunchKit - Open Source - A popular suite of developer tools, now 100% open source.