Since I installed it, Akisment has blocked 100% of the droves of unprintable comment spam that streams into my site on a daily basis, effectively eliminating comment spam as a problem and hinderance to managing my blog.
Akisment is a production of Automattic labs, the newly-formed company behind WordPress. It’s a cinch to install and use on your WordPress blog- just grab the files, upload them to your /plugins/ folder inside your WordPress install, and then grab a free API key for the service by singing up for an account at WordPress.com (a free, hosted installation of the WordPress tool).
With Akismet activated on your blog, the service begins working right away. Each time a comment (or trackback) is submitted, the service reviews it according to a centralized list of spam parameters and then decides to pass it to you or hold it in your own queue. You can check your Akisment queue and remove false positives, or leave the service alone and let it delete the spam for you every 15 days.
I have a feeling that a big part of Akismet’s success rate is that it is powered by the collective experience of all its users. For example, when checking your particular blog for spam, it relies on an algorithm that is ehanced each time it is put into use. So the more people that use Akismet, the more it learns about blocking spam, and the more effective it becomes for all.
Akisment was built for WordPress, but the developers have released an API with the intent that anybody who accepts comments on their site- be it blog, news site, whatever- can take advantage of the service.
If comment spam has become an unmanageable task for you, I highly recommend you try Akismet today.