Tabber Beta is a new service that allows you to import and add friends/contacts from webmail such as Gmail, Yahoo!, Windows Live, etc or from online social networking websites such as Blogs, photo galleries, RSS feeds, del.icio.us, Digg or MySpace and view their activity at the above mentioned services in real time. You can also file and search your contacts using Tags.
Apart from that, it also functions as an online adress book similiar to Plaxo wherein if your friend joins the network, any changes to his or her contact information would be reflected in your Address book.