Brendan Tompkins released CAPTCHA for CommunityServer 2007:
I'm happy to announce that CodeBetter.Com is carrying on the legacy of CAPTCHA for Community Server. CAPTCHA for CS2007 is the next generation of CS Guru Dave Burke's most excellent CAPTCHA control for Community Server 2.1. This version is implemented as a Control Adapter which allows CAPTCHA to be added to Community Server site-wide without touching any ASPX or ASCX markup code.
You can get the dll and source code here.
The installation is pretty easy since Brendan leverages the same technique as I did for my CS2007 coComment support: by using ControlAdapters not a single page or control must be touched.
In the past I always hesitated to use CAPTCHA on my blog because it´s an additional obstacle a commenter must overcome. Adding this hurdle seemed like a capitulation. But because spam has taken the upper hand over all comments I get, and CAPTCHAs are commonly used everywhere so the regular visitor is used to them, I´ll give it try and add Brendan´s CAPTCHA to my blog.