I have Camtasia and use it often...what I haven't done is research free alternatives on the Internet that my students can use. Of the 'freebies' listed in the Library2Play post, I think I like Jing the best.
Thanks to what I've learned about the freeware, I'm excited about the possibilities of using screencasting with my students this coming year. I would like to see my students create screencasts that illustrate what they are learning in class. Those screencasts can then be used as tutorials for other students...and...it I can use them as an assessment tool.
Here's the screencast I created for this post. I did this without a script, so there are a few mistakes, but in all, I think it's okay!