Here's an example Chemistry video, done for BCLN by Darrol Colgur using Camtasia. Darrol has fantastic audio in his videos - few teachers have such a good "radio voice." He also makes good use of a pointer (yellow arrow) to help students follow along with his discussion.
Here's another example Chemistry video by Darrol using Camtasia. Darrol has been experimenting with some animation features within ppt - also using "Tweeny for Powerpoint" ( http://www.pptalchemy.co.uk/Tweeny.html ).
Here's an example Physics video, done for BCLN by Mike Richardson using Camtasia. Some of the interactive media pieces available on the Internet (eg. PhET) are fantastic for students, but they're a bit difficult for students to really "get a feel for" without some guidance. I've found that when we have a interactive media piece in a course, a quick discussion/introduction prior to the piece makes it a little more approachable by most students.
Here's another one by Mike where he mixes sample problem solving with media exploration, done for BCLN using Camtasia. Again, very effective use of existing media. The students are much more comfortable doing their own experimenting, following this lead.
Here's a conceptual example Physics video, done for BCLN by Brent Sawatzky using Captivate.
Here's another example Physics video. It uses the Captivate highlight feature a lot - another way of allowing students to follow along with the discussion reasonably easy. Decide what works best for you.
Biology examples look a little different than the Math/Physics/Chemistry ones in that the explanation is not as much of a problem solving process as much as a visualization. Here's an example done for BCLN by Toni Kormish using Captivate.
Here's a visual math example, done for BCLN by Lynn Hadfield using Captivate. This is the type of discussion that is very hard to "get across" to a grade 6 student via text.
Here's an example of one where it's a mix of the standard blackboard background and software demo. It was done for BCLN in Captivate by Barb Boonstra.
Here's an example of a video for Math 8. It was done for BCLN in Camtasia by Duncan Millar. Great audio, and I really like his "side note."
Here's an interactive example done in Captivate.