Add an extra 2 reCAPTCHAs on the register page when someone enters a gmail email address.
reCAPTCHA on all posts on auto reCAPTCHA on all posts pending admin validation
If CAPTCHA failed 2 or more times, put on moderation queue (no matter where it is failed), if failed 3 then block changing password and email if 4 then block ACP and MCP access for that user...
Make sure they all have Enable/Disable Options on them though...
When Over 7 links in a post are made Moderators and Admins get an email. If this happens in two posts in 10 minutes, they receive a warning and 1 hour ban...
I personally think this isn't needed as there's alot of good anti spam mods that actually prevent this from happening before hand. It'd just be an advanced mod for nothing that will most likely cause errors with 3.0.6.