By far my most popular--or at least, most searched--post is the one I wrote on free screencasting tools.
While I use Camtasia for my serious screencasts, I still mourn the loss of ScreenToaster, which was a quick and easy tool, and great for students.
It's not new, but Screenr has changed enough that it's time for a re-visit.
Screenr is dead-easy to use. Just click record, adjust the frame to cover the appropriate area of your screen, then click the red button when you're ready to begin. It also has a Pause feature, which is nice.
You can share the video with YouTube, Facebook and Twitter, or download it as an mp4, which means you can then edit it in iMovie or MovieMaker to add titles, screen credits, etc. Another nice plus.
It does not have the ability to add call outs, which is a shame, or even to make your cursor a bit more noticeable.
Nevertheless, this is a good, simple tool, that would be easy to use with students. Well worth a try!