Over the past year+, I've noted an incredible increase in form spam through the various web sites that I've authored and continue to manage.  As a result, I've had to go back and add CAPTCHA controls to the forms in some cases.

I'm working on a new .NET project called ArtOverture and needed to dig into a .NET based CAPTCHA control.  Looking around at the source code for dasBlog, I learned about Jeff Atkins CaptchaControl.  It's written in VB.NET for Visual Studio 2003 and ASP.NET 1.1.  However, I found that you can include the compiled DLL just fine as a toolbox control in Visual Studio 2005.  The control works perfectly without any need for recompiling.

Here's the link to Jeff's Code Project writeup on CaptchaControl.  Full source code is available.

 http://www.codeproject.com/aspnet/CaptchaControl.asp