Security Note:  The following is only available if a user has the "Moderator" permission level in the People list of the workspace.  If you are concerned about accidental exposure, you should only give users the "Moderator" permission if they understand and can handle the responsibility of setting folder or page security.

Folders can be set to "public" to make the contents inside them available without logging in.  Please be careful when setting a folder as public, as all information inside a public folder will be exposed on any page or file with default security set.

To set a folder as public, first, hover over the folder name and select "Security" on the pop-up menu  

If you don't have access to this button, then you are not a Moderator on the workspace.  Only Moderators can set the security of any page or folder on a workspace.  Check the "Users" tab to see your own role on the workspace.

Note:  Next, you must choose both the "Custom Security" radio button AND the "Make this folder public" checkbox for this security to be set.  The content inside the folder will now be accessible to anyone on the internet.