ESPECIALLY FOR TEACHERS
There is a wealth of historical recordings available to stream... It can be found at: http://www.loc.gov/jukebox/
This website is a non-profit and offers free e textbooks that are easy to download as pdfs or for droid, ipad, and kindle.
What makes this site unique is that the textbooks are offered as "flexbooks", meaning that as a teacher, you can create a free account, and then assembly your own book for classroom use by taking chapters from various books. They have student editions, teacher editions, lab manuals, and study guides. Mostly Science, Technology, Engineering, and Mathematics, but also some good resources for SAT test prep, etc.
Please visit: http://www.ck12.org/flexbook/
I would start by looking at the quickstart guide: http://www.ck12.org/about/vid-quickstart/