If you purchased a new Insight in 2006, then you can claim a tax credit on your 2006 federal taxes. I'm not sure exactly what the amount is, because the laws just changed. TurboTax or a tax adviser would be able to tell you.
There isn't any tax break for your California taxes though. It only benefits your federal taxes. Also, this only applies to new cars. If you bought the car used, then there is no tax break.