Modern browsers such as Firefox and Chrome are able to shutdown and restore the same group of tabs they had before the next time you open them, and even sometimes remember additional tab state such as scroll position within the tab.

I would like ideally to be able to select a group of tabs (about some coherent theme, perhaps) and save them away into some kind of "folder" that I could later open independently, without opening any other tabs. Obviously I can use bookmarks for this, but bookmarks are kind of old-fashioned. It would be excellent if it could also record forms that I had filled in but not submitted, scroll position, tab position within the tab group, and any other "dynamic" aspects of the current tab state.