Pocket - When you find something you want to view later, put it in Pocket.
Zorbi - Spaced-Repetition Flashcards - Other tools are built by boomers, Zorbi is built by students.
Raindrop.io - All your articles, photos, video & content from web & apps in one place.
Mochi - Write notes and flashcards with Markdown and study them with spaced repetition.
wallabag - Save the web, freely.
SmartCards+ - Spaced Repetition Software for iOS. Modern, powerful and easy to use.