Comment Guard Pro is finally turning out to be the uber anti-comment spam protection plugin I dreamt of; everything you would ever want in a comment spam protection plugin and more, much more. The plugin itself is composed of several modules, each of which can be individually enabled / disabled, tweaked and configured all from the user interface. You can easily write your own modules or pluglets too. It addresses all forms of comment spam including regular comment spam, trackback spam, referrer spam and pingback spam. It will ship with over a dozen pluglets (small plugins) for filtering spam. We are in the final stages of development, adding few plugins, making the UI nicer etc. The documentation (my bane) is yet to be written but I have found a volunteer this time around.