I noticed an integrated Calendar notification and a tabbed news summary page in my Yahoo! Mail Beta account. The Yahoo! Mail Blog mentions they’ve launched a new version of the Beta with the following features:

Integrated Calendar
The new calendar timeline (A notification icon that appears at the bottom of your Yahoo! Mail Page) is like a ticker view of all your upcoming appointments.

Smarter attaching
Now you can attach a big file and continue working. Files upload in the background - This is a very useful improvement

Spam and Size columns
There’s a new colum in the Inbox next to Flag for Spam. So if you get a spam message in your Inbox, no need to right click on the message and choose, This is spam. Now you can just tick the Spam box against the message. You can also view the size of a message in the Size column

-New Options
-Also a few performance improvements for faster scrolling and composing in Firefox, Search, etc