I added Mollom comment spam suppresion to Feather the other day. It is actually in place right here on this blog. Truthfully, you can't see it from the outside, but you'll have to take my word for it. Or go get a Feather install of your own and add the plugin by going to Plugins -> Install Plugin -> "http://notch8.com/feather-mollom", plugin your Mollom keys and off you go =-)
All the plugin does right now is ask Mollom's servers if a comment is spam. If it is the comment is saved, but not posted. If it is not spam then it is posted directly. There is more technology that Mollom offers, but if you want that then grab a fork on Github and get to work!
