Linux Version of Windows 7 Libraries

"Things that I found, that seem to do what you need:

metatracker with trackerfs - seems to be the best choice
tagfs - might be not as comfy as metatracker
leaftag - didn't find version that's new"

"In Linux you can use hard and symbolic links to create virtual directories.

Taken from Windows-to-Linux roadmap: Part 2

A link
is a reference to a file, so that you
can let files be seen in multiple
locations of the file system. However,
in Linux, a link can be treated as the
original file. As far as other
applications on the system are
concerned, a link is the original
file. When you make edits to a file
through the link, you are editing the
original. A link is not a copy. There
are two kinds of links: a hard link
and a symbolic link.

A hard link can only reference files
in the same file system. It provides a
reference to the file's physical index
(also called an inode) in the file's
system. Hard links do not break when
you move the original file around
because they all point to the file's
physical data rather than its location
in the file structure. A hard-linked
file does not require the user to have
access rights to the original file and
does not show the location of the
original, so it has some security
advantages. If you delete a file that
has been hard linked, the file remains
until all references have been deleted
as well.

A symbolic link is a pointer to a
file's location in the file system.
Symbolic links can span file systems
and can even point to files in a
remote file system. A symbolic link
shows the location of the original
file and requires a user to have
access rights to the original file's
location in order to use the link. If
the original file is deleted, all of
the symbolic links become broken. They
will point to a non-existent location
in the file system.

Both types of links can be made with
the command ln . By
default ln will make a hard link. The
-s switch will make a symbolic link.

Create a hard link from MyFile in the current directory to /YourDir/MyFile
ln MyFile /YourDir

Create a symbolic (soft) link from MyFile in
the current directory to /YourDir/YourFile
ln -s MyFile/YourDir/Yourfile

In the above examples, MyFile,
/YourDir/MyFile, and /YourDir/Yourfile
are all treated as the same file."