A gravatar is a small avatar image that will automatically show up next to your comments on any site supporting gravatars. Like this one.
Here's how to set one up:
1. Go to http://site.gravatar.com/
2. Follow the directions there. The important part is to use the same email address you use when you post comments (and the same email address you use to register to post comments on sites that require registration).
3. Post comments on gravatar-enabled sites, like this one.
If you use a rude gravatar, we will hurt you.