I love free tech! I have been using http://www.screentoaster.com/ to create videos of some of the more difficult multi-step things that I teach. It’s pretty good; however, the viewer can’t control the playback except for pause and play, so if the miss something they have to start over. I will probably start downloading the videos once i record them, and republish them somewhere else so that students will have the option to go back over things I have missed.
I also use videos from many other sources: including freevideolectures.com, TED.com, and youtube.
I also use several resources from http://www.wisc-online.com, and many other sources.
I have students use google earth, as well as sketchup as well, and will probably be adding other opensource programs.
I think for k-12 the resources at http://www.childtopia.com/index.php?newlang=eng and http://phet.colorado.edu/index.php are very good. I will be adding these to my son’s list of websites (he’s 3). I think there are several at childtopia that he could use.