I logged into my Yahoo! mail account today. It's one I use for spam and dummy accounts, plus I insist on having at least 8 active email address because it keeps things interesting. Anyway, I logged in and was prompted to try the new "Yahoo! Mail Beta". It's actually very slick. It's a full AJAX email client.
The first thing you notice is that it's not a Gmail clone. It looks nothing like Gmail, and really acts very little like it. It's more of a web-based Outlook or Thunderbird, and has a "desktop app" look and feel. Anyway, I didn't use it much, but it has a so-so RSS reader built in and seems like a good application. To bad it will never get any market share back from Gmail.