For those that use WordPress a must to fight spam on their blog is to enable the Akismet plugin. But all Akismet does is hold all the spam and allow you to delete it, it doesn’t help you fight spam. A new plugin that has been released now will help you fight it, by finding the worst offenders listed in Akismet, it will then ban those ip addresses that the spam is coming from. Using this plugin should cut down your spam by large amounts, but like all anti-spam software, always watch it closely the first few months, you may be stopping or deleting an important message.
grab the AkismetWorst Offenders Plugin at http://boakes.org/akismet-worst-offenders