Our instructors love using Camtasia screen recording software to create lecture videos. Typically instructors create videos by recording their screen and microphone with Camtasia while delivering a slideshow lecture. The people over at Camtasia have a great product and have excellent support resources available for both Mac and PC. They also provide great email and phone support and will even hand-hold you through your first video recording if you contact tech support.
We recommend that all instructors use Camtasia regardless of experience. It is available for both Mac and PC and cost $249 but comes with a 30-day free trial, so you can create your first few videos for free.
Mac Only: QuickTime Version 10.x (Version 10 or higher. May not be available for older Macs). This is free as long as you have this version or higher. Upgrading, if necessary typically costs around $30. QuickTime has a very simple process for creating screen recordings, but it does not have the editing capabilities that Camtasia offers. You also loose out on Camtasia's fantastic support, so please only choose this path if you are comfortable googling for tech answers.