Ezvid is a free screen capture and video editing program. You can create your instructional videos with this program, and the interface allows you to uploading and share videos to YouTube.
A great and free alternative to Camstasia and Adobe Captivate, and its simple and easy to use for both teachers and students, they company has also a very informative site, with easy to follow tutorials.
Anyone can also use the program outside of the classroom.
Well my son told me about this software as apparently gamers use it to also record videos games (in game play), making it ideal for creating game play tutorials for PC video games.