I’m messing with the gravatar plug-in for the comments. Basically, if you go to their site, and upload an image to associate with your e-mail, it will display that image whenever you use that e-mail address to identify yourself with a comment.
Update – Brenda posted this in the comments – I had a similar problem:
After I selected my 80×80 icon and hit crop, I had to also assign it to the email (seemed like it should do it automatically, but it was a second step).