tree-style bookmarks for Emacs?

[Terrence Brannon]

There is an excellent Firefox add-on called [Tree Style Tabs](https://
addons.mozilla.org/en-US/firefox/addon/5890/)

I have a desire for similar functionality in Emacs, so that I keep a
folder of bookmarks and when I open that folder, all the files that
are pointed to by that folder open in a tree, as shown in this mocked-
up screenshot:

http://www.screencast.com/users/terrence_work/folders/Jing/media/d550ae5f-e279-4468-8d1d-00c5c75bc77d

In a sense, the ecb history buffer allows tree-based selection of
files, but the parent of the tree of files, it based on a directory,
not based on a folder that I choose to organize a set of files into.