Akismet is a new comment spam defeating system designed by WordPress creator Matt Mullenweg. Instead of filtering all comments locally, each comment’s data is sent out to the Akismet servers and tested among spam for other sites to create a far more accurate judgment of it’s validity. The only prerequisite is a WordPress.com API key, which can be signed up for at their site. Installation couldn’t be simpler, too. Per their public request, I’ve disabled other comment spam plugins such as Bad Behavior (which may or may not fix RSS issues a few people are having). So far, I’m quite impressed with how easy it is to use. Time will tell if it really works. If you’re interested in using it on your own site, you can check out their FAQ, or go right ahead and download the WordPress plugin.
Update: It’s been 15 days since I activated Akismet and disabled all my other comment spam plugins, and so far I’ve seen only one unmoderated spam comment, while Akismet has blocked 1477 others. Those are impressive results! Also, WordPress.com is out of beta for those interested in getting an API key.