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.

Here's a video overview of its features: https://www.youtube.com/watch?v=OqjcrfKjobY

* I haven't reached the maximum yet...

[1]: https://chrome.google.com/webstore/detail/tabs-outliner/eggk...

[2]: https://code.google.com/p/chromium/issues/detail?id=51084