I use tabs instead of bookmarks. Opera also has tab groups, so I can drag one tab to another to create a collapsible group of tabs related to a particular project. It's not unusual for me to have a handful of tab groups with a dozen of tabs in each, plus half a dozen of regular tabs for what I'm currently reading. The only down side with this is that browsing is slower when I just have started my browser and I'm waiting for all the tabs to load, but I don't close my browser that often. [Edit: apparently there are startup speed improvements in Opera 12 specifically for the many-tabs-open use case]