The Akismet WordPress Plugin is awesome. I was up to a couple of hundred or so spam comments a day on various WordPress hosted blugs, and it was getting to be quite a waste of time deciding what was a real comment of a wonderful gift of spam.
Downloading and installing the Akismet WordPress Plugin was simple. Â Directions can be found on their site, it took me probably 5 minutes to get the whole think up and running. Also necessary for the install is a WordPress API key. Â This can be gotten from the WordPress. Â
Again, if you have a WordPress powered blog install the  Akismet plugin now.