I somehow haven't noticed the form of spam avoidance than Joe Gregorio uses on his blog.
Instead of asking for some inane piece of information (CAPTCHA) he simply asks for your name and email || website in a special format: bob (email) or bob (websiteurl).
This is so simple and smart in that most blogs ask for this anyway, but it is different enough that spam bots won't know about it yet (hopefully). If they grok it you can just change the format (e.g. bob [email]).
More hackable than a "your site specific" logic CAPTCHA, but it does have the nice effect of being obscure, and hopefully it will stay that way.