Is it scrap gold, bars/rounds or coins with potential numismatic value? If you find a good local gold buyer, you can negotiate spot or even slightly above spot. I would also suggest using craigslist or local gold forums in an attempt to maximize value. Also, try Tulving.com. He offers very competitive pricing on buys & sells.
I have seen those kiosks in the malls buying and selling gold, funny thing is they starting popping up everywhere just about 6 months ago, who knows maybe that meant it was a sign of a top, maybe they will be willing to buy all your gold bars for 1500 an OZ.
You will get the best value if you can find another investor that is willing to buy the Gold at the spot market price at the time your doing the transaction. Then you both benefit from a neutral price.
Honestly I think Apmex is the best place to sell your gold if its not scrap. I just did a quick search and they buy kilo bars for about $5 per oz under spot, so thats a pretty good deal and all it takes is one phone call and you just ship it. You could sell on ebay and you would get more than spot price, but after you subtract ebay fees and paypal fees, you will more often than not get way under spot and its really a hassle because I sold a couple 12 oz coins to a guy and he bitched because they had scratches even though I stated in the auction it had dings. He wanted something like a 10% discount to what he paid. I told him send them back if he didnt want it but he didnt because the price went up pretty fast after that. Basically ebay is just too much of a headache. Selling to apmex is fast and you usually get a check in about 2 weeks. And really...you are only giving up $5 of spot price which is nothing. Never sell to cash for gold unles its really a small amount of gold. I found a small earring and a 14k gold ring on the ground once and sold it cash for gold for $34. It was about 1 gram of gold alltogether, so they do make about 30% off spot (gold was $50 per gram at that time)
BullionDirect runs an exchange ("Nucleo") which can be used to sell to other investors. Easier than dealing with people on a personal level, and better prices than going to a dealer.
I've actually used Nucleo them to sell a bunch of junk silver that I bought locally. They send out this prepaid metal bucket which you then drop off at Fedex. It's a functional system, not the fastest but reasonable timing.
Those retail kiosks will generally try to bid around half the current spot price (and you know what? the general public will hit that bid).