Are.na

Are.na is a platform for connecting ideas and building knowledge. You can build simple collections of content by adding links and files of any kind. Connect ideas with other people by collaborating privately or building public collections for everyone. With no ads, likes, or recommendations, Are.na is a more mindful space where you can work through any project over time. It's a place to structure your ideas and build new forms of knowledge together.

Screenshots from Chrome Web Store

Screenshots from Mozilla Add-ons