There are tons of free Android apps. I just haven't found a good source to find out which ones go free today - yet. I'm looking. (If you know of a good, reliable source, especially for education related apps, please let me know.) In the meantime…
https://market.android.com/details?id=apps_topselling_free&hl=en
http://www.androidfreeware.net/
http://www.cio.com/article/695175/Best_Free_Android_Apps_of_2011
http://www.techsupportalert.com/best-free-android-apps.htm
http://www.freewarelovers.com/android
http://www.mobileappsgallery.com/free-android-apps/
You can also go to Amazon.com and search for "free android apps" or "free android app of the day"
Hope this helps! Nathan Smith