Extensions can be managed and new ones added from Opera’s menu which take the user directly to http://addons.labs.opera.com/addons/extensions/, the page where extensions are hosted.
Already 16 extensions are available for immediate use. Some of these include YouTube downloader (at last), Yr.No Forecast (weather add-on) and Translate that “Automagically translate foreign web pages into English”
Documentation for developers on building Opera extensions has also been posted. Opera says that developers who have already authored extensions for other browsers need only tweak their codes a bit to make it compatible to Opera. I’m a bit sceptical about this claim, though.
Opera 11 alpha can be downloaded from http://www.opera.com/browser/next/. While you wait for the 9MB download to complete, take a look at these screenshots.