Although Apple's Aperture confines its internal library to a single drive, you can use a little under-the-hood trickery to span the library across multiple volumes. Completedigitalphotography.com has released a simple, free application that performs this trickery for you, allowing you to increase the size of your Aperture Library.

With a single click, the Aperture Library Spanner reconfigures your Aperture library so that it is stored across several currently-mounted volumes. If you later decide you want to return to a normal, single-volume library, you can easily undo the change from within Aperture itself.

The Aperture Library Spanner is available for free at: http://www.completedigitalphotography.com/?p=417