There have been a couple of attempts to establish a valley-wide Camaro club of sorts, but neither have accomplished long-term success. I've met many great Camaro enthusiasts just going to nearby cruises and saying hi.
If you haven't already discovered these on you own......
http://www.cruisinarizona.com/
This site is not working properly right now, but should be OK soon....
http://www.desertcruisers.com/