Prism
This site allows you to import a text or problem, give students a prompt or guided direction and then receive their responses on the text. As more students respond to the various questions, the text gets larger showing the comparison of answers on the screen. A great resource for getting students to respond to a text.
Evernote
This notetaking site allows students to incorporate audio, images, video, links, etc. seamlesslly into their notes.
Wolframalpha
This is an automatic "knowledge" calculator. It will give factual information on an entire range of topics from Shakespeare to the Civil War to calculus to languages.
Quizlet
This allows teachers and students to create study sets of words, concepts, etc. for studying and referencing.
Kahoot
This website allows teachers to create quizzes for students to take on any device. Instant feedback is given to students and teachers.