I am trying to get used to using Opera's Tab Stcking to arrange pages from a site.
For instance, using WebmasterWorld as one tab, Bing as another, PubCon, and Twitter as another. It seems like this should work 'in theory', but I have yet to get a grasp on the usability here. I am always trying to 'find that page'.
I mostly use tab stacking during research. I stack the tabs related to one task and they're all in one spot while I go off on another task. Then hovering on a stack's tab shows me a preview of all the pages in that stack which helps a lot.
What would make this a more useful feature for me would be a way to label a stack. Then one look at the toolbar label would tell me why I built that particular stack. That sounds like a pretty complex UI to develop, however, so I'm not holding my breath.