Wolfram Alpha is a FREE online computational knowledge engine. Ask it anything and it will throw up answers quickly,in real time. All systematic knowledge is immediately computable and accessible. Watch the introductory videos showing you the examples. Access on internet or mobile phone and calculations of any kind as also data of various items are at your finger tips. I particularly liked finding out where the ISS or International Space Station is at the moment and the step by step calculations in Math and Chemistry.
Wolfram Alpha in the classroom for their students.There are plenty of resources for the educator and ideas to implement thereby supplementing classroom teaching.