[Ruby] Recommended anti-spam controls - was Re: RubyHolic Down

[Dave Myron]

>
> I'm gonna need to start putting anti-spam controls in there. :(
>

Hijacked! This has been floating around my brain for some time and  
would like to make a lazy-web request:

What are some recommended anti-spam measures that are low-impact  
within the confines of Rails?

In some places I've used a hidden form field whose value must be  
blank upon submission and this has helped filter out many spam bots  
since they tend to give every form field a value, even hidden fields.  
I'm curious about Rails-friendly captcha systems though. Seems like  
there are several out there; has any one a recommendation?

Dave Myron
Eachday