Monday, August 29th, 2005p>Vivek Jishtu has written a Firefox extension that adds Ajax support to Yahoo! Mail:
Adds AJAX support to the current Yahoo! mail and makes it a little more friendly. You can preview your messages without leaving your inbox. It adds a small arrow next to your email list. Click on the arrow to preview the message.
Currently the Instant Reply is being developed. I will update it as soon as possible or if I get enough people who want it.
Here you can see it in action:
( via Guillaume )