Captcha is a nice anti-spam technique for websites. By forcing a user to enter a word that is a bit scrambled on the screen you can eliminate a large amount of spam that you would otherwise have to manually fix. reCaptcha is a free service that provides captcha functionality through an API. That’s what I’m using on this site and to be honest what I’m growing quite fond of. At this point I’ve leveraged it for about 5 sites in the past month and all have seen a dramatic drop in spam over previous techniques I’ve tried. This has been across Joomla!, WordPress and the latest: MediaWiki. The ConfirmEdit Extension for MediaWiki makes it pretty simple to install and get up and running. Check it out here.