Very good presentation by Aaron Hansen and Ray Birks of Wenatchee School District from 10/2012.
http://waetag.tk/
Their presentation includes websites and iPad apps, for K-12. Here are some free ones that I thought especially useful for high school and that people may not have heard about.
Sites
PollEverywhere -- polls taken via phone, web and Twitter -- use it as a clicker response system
FlockDraw -- draw collaboratively -- on the same page at the same time
Scale of the Universe
Speak Pipe -- record a voice message and email it (up to 10 minutes)
Sound Cloud -- record audio files and share
Soundation -- site for creating music (aka free Garageband)
iPad apps
History: Maps of the World
3D Cell Simulations
Coaster Physics
Science 360
Woices -- geolocalized audioguides done by users around the world - record one or explore others'
