Devhints is a set of useful cheatsheets displayed in a stylish way
Copy Code is an extension for Chrome that adds a button to the code snippets on Stack Overflow and other sites making it easier for you to copy code snippets in one click.
Slicki - The Wiki For Slack lets you create and maintain wiki pages linked to Slack channels.
Use it as an intranet, as product documentation, or as a place to store things you shouldn't forget. It's a great way to build documentation from conversation, and to easily store and retrieve information relevant to certain groups in any organisation.