Annotate.tv - Optimize your learning on YouTube
Pocket - When you find something you want to view later, put it in Pocket.
Mochi - Write notes and flashcards with Markdown and study them with spaced repetition.
Raindrop.io - All your articles, photos, video & content from web & apps in one place.
Jot - The no-fuss way to take notes
Tettra - Tettra is a company wiki that helps teams manage and share organizational knowledge.