Document libraries are a great way to manage and organize documents, and one of the many benefits of leverage SharePoint for document managements is to have a central repository for documents.  File shares are prone to duplicate documents and multiple versions of the same documents, and obviously using SharePoint will mitigate many of these concerns.  Occasionally though, it makes sense to keep a document in multiple locations – what if for whatever reason, a document belongs in Library 1 and also Library 2?  Should you just upload it to both places?  Nope!  Utilizing a built-in content type will allow you to create shortcuts that point to the original location in your document library.

To illustrate this, I’ve created an Expense Reports document library with a few entries. Granted, expense reports probably aren’t a practical example, but I couldn’t think of anything more creative :).

As you can see, the actual documents are stored within this library.  Next, I created a My Shortcuts document library that will be used to store documents or shortcuts to other documents.  After creating the My Shortcuts library, you must allow the management of content types by navigating to Site Settings > Advanced Settings:
 

Next, add the Link to a Document content type to the document library:

 
Once you add this content type, you will be able to create a link from the New toolbar menu:

Simply enter a name for the shortcut and the URL, and click OK:

Viola!  A link to the document!

This is a great way to keep your documents in a single place, but still be able to provide a link to it from within a completely separate library.