Screencasting or Screen capturing is the process of capturing activities on your computer screen that will be played back by other users. It may include audio and annotations and is often used for creating online tutorials and training videos.

There are plenty of video tutorials on YouTube and people are using them to demonstrate almost anything. If you want to create video tutorials the good news is that you can do it for free. There is no reason why you can't create perfectly good screen casts for free. The commercial products give you more creative options but these are really necessary if you are creating videos for commercial purposes.

My favourite is CamStudio but it is worth looking at the others and compare their features. Which one suits your purposes really depends on what you are trying to demonstrate in your tutorial, who your target audience is and whether you are getting paid. If your videos are earning you money then spending $150 on Adobe Captivate may be worth it do to its excellent post-recording editing capabilities.

Free

The following screen capture products are completely free.

CamStudio.org
http://www.camstudio.org/
An open source program for capturing on-screen video and audio. It captures as an AVI and includes a custom codec resulting in quality videos. CamStudio only works on Windwos but is completely free. It has various options for defining the region to capture, highlighting your mouse cursor and button clicks as well as allowing autopanning. It has no editing capabilities so once your video is captured you will have to use other tools to cut/splice or edit.

Screencast-O-Matic.com
http://www.screencast-o-matic.com/
A Java-based screencasting tool that runs on your PC. It runs on Windows and Mac but has some issues with Linux. Once you have created a video you can either save it locally or upload to their hosting site.

Wink
http://www.debugmode.com/wink/
This software that works slightly differently to the others listed in this article. Rather than video it creates screencasts by you taking screenshots of your activities. These screenshots can be organised and annotated. In a way it is more of a slideshow rather than a video. Outputs to various formats including Flash, PDF and HTML.

I've used all the above the produce various tutorials and video demonstrations. The only other tools you might need to look at are VirtualDub for cutting and joining video

Commercial

The following options are commercial products. They offer lots more functionality but that functionality comes at a price. Where it is worth it depends on the videos you are creating.

Adobe Captivate
http://www.adobe.com/products/captivate/
As you would expect from Adobe Captivate is a fully featured screen capture and authoring package. It is likely to do everything you could want but it comes with a $150 price tag.

Camtasia
http://www.techsmith.com/camtasia/
Camtasia is a screen recording and video editing system for both Windows and Mac. Once you've captured your on screen action you can add and edit sound plus a range of annotations.