There are several different WordPress Plug-ins that help reduce comment spam on your blog, but one of the best ones you can find is WP-SpamFree. This plugin works differently in that you have more control over the filtering than you do with the Akismet plug-in and this plugin allows you to log all comments so you can be sure you are only catching SPAM and make sure that false positives aren’t being blocked.
The other thing you can do is set and modify your Your current WordPress Comment Blacklist in the WP-SpamFree Options. This allows you to create a custom list of “keywords”, “emails” or IP Addresses that will automatically be blocked in the future. So if some specific IP’s or emails keep getting through your existing spam settings, you can blacklist the IP that the spam is coming from. (Use with caution as you can unintentionally block others if you put entire IP subnets or keywords that could be found on normal comments.
WP-SpamFree also comes with a built in Contact form that allows you to embed a contact for on your blog, you can customize fields and as well. It isn’t powerful or overly customizable, but can be useful if you want one plug-in that does both functions.
In my own testing I found that WP-SpamFree combined with Akismet both were an ideal way to block nearly all spam comments to your blog. Akismet alone will leave lots of comments in your Pending or Spam Bucket. WP-SpamFree will block the spam and you will never have to go weed through your pending or spam comment areas so it saves you time.
Don’t take my word for it, you can find a really good review of WP-SpamFree over on StrictlyOnlineBiz with screenshots of the plugin settings.