What if you could share Aperture libraries without using your own server?  The use of Dropbox in this set of instructions automates the process of backing up and sharing Aperture libraries for you (set it and forget it).  This is a “cloud” (off-site) solution.  To use this three-step process you MUST (as in do NOT do this if you have not) exit Aperture before doing ANY of it.  Here’s how:

1. Move ~/Users/my_user_on_the_system/Pictures/Aperture Library.aplibrary to /Users/my_user_on_the_system/Dropbox.
2. Create an alias of /Users/my_user_on_the_system/Dropbox/Aperture Library.aplibrary.
3. Move the alias of the Aperture Library back to ~/Users/my_user_on_the_system/Pictures/

What this does:
All Aperture library files now exist in Dropbox AND on the computer.  If anything goes wrong (HD fails), recover Aperture libraries by reinstalling Dropbox (on the new HD/OS/Computer), syncing Dropbox, and repeat step 3 (above).  As it is just a symlink, you do not have to wait for files to move.  They will have already moved from the cloud (Dropbox) back to the computer.

Some notes:
As an example the home network uses a MacMini as a server.  OpenDirectory is running.  Users on the Laptops in use are local network users.  This means that a copy of each users /User folder (and Libraries among other things) are on the server.  This way any user can log in to the same account on the desktop, server, and the other laptops in the house.  Aperture and Dropbox are running on each machine (with the same configuration).  At this time there is a copy of the Aperture library (for each user) on each Laptop, on the server, on the Win7 part of any Laptop (I’m unaware of an app that can open an Aperture library however), and in the cloud in Dropbox.  That means it’s spread across 3 different computers, 2 different OS’s, and 2 different cloud services (remember I use iCloud too).

There is another method for pointing Aperture directly at the new library location.  If you MOVE the library to the DropBox directory stated above, and then start Aperture, Aperture will ask you for the current location of the library.  The advantage is that you don’t have to worry about a symbolic link breaking.  The disadvantage is, if you have other Aperture libraries, Aperture will prompt you to use one of these.  It is assumed that if YOU created more than one library, you know which one you want to use.

**As always YMMV.  Do NOT attempt to use this as a method for having two or more people edit the same photo in the same library at the same time.  When one editor saves the photo, the next editor will overwrite the previous save.  You CAN use this as a method for multiple people to display photo’s in the same library.