Screencast Video Tools Options for Usability Testing
Windows Platform
Cam Studio (Free, released under the GPL Licence)
Creates AVI video files and using its built-in SWF Producer can turn those AVIs into bandwidth-friendly Streaming Flash videos (SWFs)

Debut (Free)
Compatible with Windows 98/2000/XP/2003/Vista. Records video in many different file formats including .avi, .wmv, .asf .mpg, .3gp, .mp4, .mov and more.

uTipu (Free, share online)
Compatible with Windows XP and Vista. Record up to 20 minutes. Saves videos in Flash Video format. Allows for zooming and still in Beta.
Mac Platform
iShowU ($20)
Comes with built-in video presets. Supports QuickTime compression. Compatible on both Tiger and Leopard.

ScreenFlick ($29)
Offers the ability to display keyboard commands, and highlights mouse clicks to better communicate which actions are being performed during screen recording. Compatible with tiger or later.
ScreenFlow ($99)
Compatible with Leopard. Powerful editing tools. Highlight using ‘Callouts’. High quality exporting.

Both Platforms
Jing Project (Free, share online)
Snap a picture of anything on your desktop. Record video of what you do, or what you see. Instantly uploaded. Share in email, IM, or blogs.
Screen-o-Matic (Free, share online)
Screencast-O-Matic is the free and easy way to create a video recording of your screen (aka screencast) and upload it for free hosting all from your browser with no install but again still in Beta.