I recently attended our Developer User Group meeting in NYC, we had a great time reviewing code and talking about Visualforce, Apex Code and Force.com Sites.
The UG meeting was held in the evening (6-9pm) at Le Meridien and more than 60 developers came out to learn about the Force.com platform, building apps and to learn from each other.
I gave a quick technical overview of the Force.com platform and spent a bit more time on new technologies such Sites and Force.com for Google App Engine. Ketan Khandkar, Principal at Navatar Group gave a presentation and covered some best practices for building native apps with Visualforce, He had a great demo for us. Thanks to Navatar Group from sponsoring this event !
One of the topics that we discussed was how easy or hard would it be to construct a CAPTCHA challenge for a Force.com Sites input form, such as those that you often see in blogs or conference registration applications.
Well, I was nothing if not curious, so I spent some time researching this and quickly found out just how easy it is to build a CAPTCHA component for Visualforce. In fact, it's so easy that I built this sample here, it took a few hours because I had to study the Ajax code provided by the reCAPTCHA project. Check out this article if you would like to learn more about input forms on Force.com sites. There is even a working example linked into my developer edition Site, you can test your own human pattern recognition skills.
Enjoy the code and let us know if you would like to have a Developer User Group in your area.