Yahoo has previewed its new "smarter inbox" for Mail, which will be able to incorporate third-party applications (Flickr, Flixster, Xoopit). You can watch a 5-minute video but it's a limited beta so you probably can't use it. The blog post says: "Only our power users, who were invited into the limited beta, can test out the new applications at beta.mail.yahoo.com." There's nothing new in my Yahoo mailbox -- and it's still very, very slow -- but you may be luckier.
Yahoo hasn't gone as far as Microsoft in the direction of Facebook-like social networking or in integrating its various services. However, it's clearly heading in the same direction.
Yahoo Mail is the world's biggest email service.