Tabs Outliner[1] is great for this. It's lacking sync (an extra top layer in the tree for each device would make sense), but other than that, it is fantastic, and has really reduced my memory usage back to normal levels. It allows you to suspend entire windows, and quickly browse all tabs. Allows for unlimited* levels of named trees/notes/windows/tabs. It does however NOT save the state of the page, only the URL.
When the Chrome Sidebar API[2] is implemented, I'm sure it will only get better, as the need for an extra window should no longer be necessary.
Checked out Tabs Outliner a few years back. Too complex for me. But it feels like once you get the hang of it, it might be useful if you fear losing those golden tab gems.
IMHO you always come across more tabs than you ever have a chance to read. And you'll always get back to them again when you actually need them via Google search.
I would love a tab sidebar. This might make Firefox worth checking out.
I've been using T.O. for about a year, and want to like it but cannot. It's semi-OK for state management, so long as you don't mind losing what you had in a particular Web page. But it hasn't made managing my tabs any easier. Not being _directly_ attached to the present browser window hurts a lot.
It also is utter pants when used with a focus-follows-mouse windowmanager policy.
IMHO you always come across more tabs than you ever have a chance to read. And you'll always get back to them again when you actually need them via Google search.
I would love a tab sidebar. This might make Firefox worth checking out.