Busy in a computer room this morning one of my year 9 (UK age 13-14) students informed me that WolframAlpha is 2 today!
I show all my students WolframAlpha in class and sometimes use it in class to check a result. I have been pleased to see students using it themselves.
See the WolframAlpha page and subpages for further details of WolframAlpha including several useful links.