PollEverywhere
polleverywhere.com
PollEverywhere is a web-based tool for live audience participation. Create polls that your classroom or audience can answer in real time, and view the results live. A free account will allow 25 responses to a single poll.
iTunes U
Available in the app store
This app is a comprehensive collection of FREE online educational resources like lectures, videos, and books. It also offers great course building tools for teachers that allow collecting existing materials and creating new content.
TED
www.ted.com
High quality videos of conferences on a variety of topics like science, technology, and culture.