Some time ago, I found this cool plugin for Thunderbird (2.x at the time) : MessageFaces (or on Mozilla Addons). It made email conversations much less impersonal by showing images of the persons that I was having an email conversation with. The beauty of the system was that I didn’t have to do anything: images were gathered from gravatar.com, X-faces, or embedded PNG images.
Then Thunderbird 3 came along, and busted quite a bit of plugins. Sadly for me, both MessageFaces and Lightning, the calendar plugin, ceased to work. Lees verder An alternative to Messagefaces compatible with Thunderbird 3