"Libraries" (a la Windows 7) on OS X?
I was looking into doing this also today, and so far the only solution I've found is to use a smart folder, hacked to search multiple locations:



What you want to do is open one of your folders (eg. /Volumes/Portable Library/Resources/) hit CMD+F and then set your desired filtering. eg. I set mine to Kind &gt; Folders. 

Save the search as a smart folder (it doesnt matter where) then open up that smart folder in TextEdit and look for the following: 

/Volumes/Portable Library/Resources/`

There will be multiple instances of the above string, you want to replace them all with new strings that contain the paths you want to search.

In your case it would look like this:

&lt;string&gt;~/Resources/&lt;/string&gt;
&lt;string&gt;/Volumes/Portable Library/Resources/&lt;/string&gt;
&lt;string&gt;/Volumes/FreeNAS Server/Resources/&lt;/string&gt;


Save the file, then when you open the smart folder it will display search results form all three folders.

If you use the column view in Finder you can move through these folders as if they are all together.



Unfortunately the downside of this is that its searching resursively, so you will get all the folders within your first three, plus any folders in those. I'm yet to find a way to disable recursive search yet...