When browsing in Safari 6 on Mountain Lion, you can use a new view called Tab View to visually explore all your open tabs.
You can access it through the Tab View button in the tab bar, or you can pinch two fingers toward each other on a trackpad.
While gestures are like the keyboard shortcuts of touch (especially on iOS), nothing is like a keyboard shortcut on the Mac than a good old keyboard shortcut.
Keyboard junkies can rejoice, as you can switch to Tab View using Shift-Command- (⇧⌘). You can then navigate using the left and right arrows between tabs, then use the Shift-Command- shortcut, or simply press the return key to select the current tab.