Sure the Contacts one isn’t that revolutionary if you are in your Mail account, but it will likely come in handy if you are out exploring another area of the Y! network.
All you need to do is mouse-over the area where your name is displayed (along with the arrow symbol) and the menu is revealed.
Just about everyone using Yahoo! Mail (Classic or the newer version) should already be seeing it there, as well as on your profiles pages, throughout* Yahoo! Groups, Yahoo! News, and more.* Be sure to keep your eyes peeled.