Shoemoney made a perl script to mail his WordPress commentors. I thought this was a great idea, but it needed to be easier to do :). I’ve quickly hacked up a php script to do this, if you put it in your wp-admin dir, you should be able to use it right away. You need admin rights to use it, you can change the from address, and insert the commentors name in the body text.
If this script becomes popular, i might add some extra stuff to it as well :)