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.
Instapaper - Instapaper is a simple tool to save web pages for reading later.
Mochi - Write notes and flashcards with Markdown and study them with spaced repetition.
WebSatchel - Copy and save web pages to your own personal archive
SmartCards+ - Spaced Repetition Software for iOS. Modern, powerful and easy to use.