Padlet - Visual boards for organizing anything.
Xmind - Xmind is a brainstorming and mind mapping application.
BookWidgets - BookWidgets is an excellent application that let you create engaging exercises in minutes and easily share a varied variety of beautiful and fun activities with your classroom and others.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Quizlet - Quizlet allows you to review and create flashcards for a variety of subjects, such as math and reading.
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.