There are other add-ons providing instant-messaging capability to Firefox, but Yoono gets the special mention here because it supports the most chat and social-networking services: AIM, Facebook, Flickr, FriendFeed, Google Talk, Imeem, LinkedIn, MSN, MySpace, Twitter, and Yahoo Messenger.
Yoono also throws in widgets for Web note-taking (such as you can clip and save text or images you find on the Web); an RSS reader; e-mail alerting for your Yahoo Mail, Gmail and Hotmail accounts; and it can stream music from Imeem or Last.fm.
Yoono installs as a sidebar set to the left of the main Firefox window. When you click a button, it slides open as a wider control panel, but, otherwise, takes up minimal space.
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