WP-SpamFree is different from most anti-spam plugins. Instead of trying to use complex algorithms to determine whether or not a comment is spam, the plugin uses javascript to weed out automated comment bots.
Unfortunately this will stop some legitimate folk from leaving comments (like users of the NoScript add-on for FireFox) but so far it hasn’t been too much of a problem with my own blog. For the total elimination of spam it’s at least worth a test.
