Gravatar is an online service where you can upload a picture and connect it to your e-mail address. When you comment on a blog, Gravatar will recognize your e-mail and add your picture as an avatar. No sign-up is required and there are no privacy issues involved.
I think it’s brilliant, and strongly recommend you guys to get yourself a Gravatar account today (some of us have it already). It works on most websites, too. I would love to see the faces of my readers and commentators! I read and answer comments several times a day, so it would also be much easier for me to recognize and therefore relate to each and every one here.