OSX program similar to 'Fences'
Solution 1:
Desktop Groups (Which I would describe as the best alternative to fences) is made by the same people who make Desktop Shelves. The product is paid, but the Lite version of Desktop Groups is free.
A good review of its features can found here courtesy of Fatima Wahib who reviewed it for Addictive Tips last month:
Solution 2:
I'm not sure its exactly what you need, but how about something like DesktopShelves (there's also a free version)?