It doesn't hurt to get a quote from local dealers (including a carmax, if local), but they will generally lowball you - like WAY low.
I do as I did, and list it on CL and Autotrader. Autotrader isn't free, but a basic listing isn't much. I ended up selling my car to an out-of-state small-time dealer via Autotrader - he came up here and got it. Other local dealers were generally $750-$1000 less than what he bought it for. One dealer eventually upped their offer to be in line with what I sold it for, but that was about four months after I had already sold it (I got a letter in the mail saying they would now offer me $X if I still had it), which was almost five months since I received the initial quote.
A lot of it comes down to how much you feel it is worth your time, more than anything.