Yahoo! added "My Cool Fonts" to its Mail to gives your email messages a personal touch. "Creating colorful emails using fonts is easy – just launch My Cool Fonts app from Applications menu, select font, type a message, click "Create email" and a new email gets created, and you can then add any other text or attachments to your illustrated message," explains Yahoo!.
Most of these fonts have its their own set of smileys, which you can browse and easily insert into your message from Smileys menu. Fontself app is now available to Yahoo! Mail users in "Argentina, Australia, Brazil, France, Germany, Hong Kong, Italy, Mexico, New Zealand, Spain, and UK."
More Info: Fonts List