Personalize, if not humanize, your posts, adding (CSS) popups containings avatars next to mailto links, as well as next to any word. You can chose avatar images, or let Gravatar chose it for you.
For documentation and tips, please refer to the official plugin page for <a href="http://planetozh.com/blog/my-projects/wordpress-plugin-avatar-gravatar-popup/" title="Avatar Popup" rel="nofollow ugc">Avatar Popup</a>

Ozh' Avatar Popup

Add CSS popups next to mailto links or next to any word. Can be any custom image, and has gravatar support.

This fun plugin just replaces the “Excerpt” meta-box with something more meaningful for the Modern Redditor.
Oh, also, it’s a neat example of custom string replacement using a filter over gettext 🙂
<h3>Support</h3>
On <a href="https://github.com/ozh/too-long-didnt-read" rel="nofollow ugc">Github</a>. I don’t read WordPress support forums.

Ozh' Avatar Popup vs TL;DR