Camtasia Studio is by far the best screencasting software – its currently available only for Windows though a Mac version of Camtasia is under development.
Related: Review of Camtasia Studio
Now a full retail version of Camtasia Studio 5 costs $300 but you can have Camtasia for free.
The only catch is that this offer is available for Camtasia Studio 3. Download the demo of Camtasia Studio 3 here and then request a registration key from Techsmith here to convert that demo into a full licensed version.
Though you may miss some of the new features like Auto Pan and Zoom, Camtasia Studio 3 will still solve most of your screencasting problems – also includes quizzing, titles, PIP and support for recording PPT presentations.