Now that the Q1 2010 release is here, I want to bring your attention to a cool new feature in our RadCaptcha control for ASP.NET AJAX - audio support. Head on over to our online demos to see the feature in action. Enabling this on an existing CAPTCHA is easy - you just need to set the CaptchaImage-EnableCaptchaAudio property to true.
Adding this feature to your site will allow blind or partially sighted people to use it as well.
The audio support presents some very interesting possibilities for people who like to customize things. For example, you can replace the original audio files that come with the control (stored in the ~/App_Data/RadCaptcha/ folder in your web application) and add some custom ones - instead of hearing simply "alpha", you can make the control ask "enter the third letter in the word boat". You can also make it speak in German or French.