Opera 11 goes to beta is available to download, The next major version of Opera came with many new features, Which includes tab stacking, lets you drag one tab over another to create a group. Now, you can keep dozens of webpages open, organized and under control, Extensions which gives you more functionality. Currently the Opera 11 extention labs contains 131 and growing.
The tab stacking can be see in the video
Opera 11 has performance enhancements, more HTML 5 support, Enhanced email in your browser and least but not the last, faster installation, the Opera 11 is 30% less in size with 10.60.
The Opera 11 beta 1 is available for Windows, Mac OS and Linux.