The newest model year would be the ZR-1 C6 - which I believe came out in 2010 - so I assume it is a model of the 2009 car. 2009 was the first year of the ZR-1 high performance C6.
The C6-R was raced in 2005 - once again assuming things, that would probably be the 2005 model car year.
The Z06, which was just re-released, is a 2006 model year.
I have been researching these lately for the Cannonball Run community build - I am not an expert so you can check my facts;).
EDIT: Casey has it correct though - AMT has the 2012 C6s out. They are the unassembled promos though, so I hadn't considered those in my research