Depends on the condition and originality (has it been reblued, worked on, customized, etc. or left in original condition).
There will be a gun show at the OC Fairgrounds January 26 - 27, 2008, and you could take it there to show a wide variety of dealers and collectors. Many of the folks there are true aficianados and will be happy to show you the Blue Book of Gun Values or other resources that will help determine its true value. True collectors won't screw you on the price.
Consignment is a good option, but you will typically pay a 20% fee. I would get several opinions, as you may have a truly valuable collector's item, or not.
Another resource is the website www.gunsamerica.com, which is a large buyers and sellers forum. The model of your pistol should be located on the slide. You can also search for Colt forums on the internet - some even allow you to enter the serial number (or they have a list of serial numbers) to determine when it was manufactured, etc.
The link Trooper provided states that you transport it unloaded, in a locked container, which could be your trunk. Doesn't sound like you have any ammunition, but if you do, leave it at home. Wal Mart and Big 5 sell plastic single-pistol cases for less than $10, and you can lock it with a small padlock. You can also get soft (cloth/nylon) pistol cases that lock through the zipper tab. The law only provides for a locked container, even one that can be cut into or has a tiny, silly padlock.
If you do go to the gun show, admission is $12, and you can transport the pistol in the plastic or soft case, locked. The gun show staff will inspect it outside the gate and put a plastic zip-tie like deal through the action so you can walk around the show with it out for inspection by dealers, etc.
