A Gravatar is a Globally Recognized Avatar. You create an account and upload your photo just once, and then when you participate in any Gravatar-enabled site, your Gravatar image will automatically follow you there. What's great about Gravatar is you can associate different photos to different email addresses so you could have one for personal and another for business.

Give it a try, get your free gravatar at http://en.gravatar.com/ and comment on one of our blog posts to see it in action.