It's a major time-killer to sift through your three dozen open tabs, looking for a needle in a tab-stack. So it's a good thing that Mozilla has given tabs some long-overdue love in the second Firefox 4 beta with App Tabs.
Available for Windows, Mac, and Linux, App Tabs are perfect for Web apps. The feature makes your must-use tabs easy to find and makes it harder to close them. Check out this tutorial to see how to use them and how they compare with the similar feature from Google Chrome, Pin Tab.