http://www.gold4bank.com/gold-companies/Provides a breakdown of what services each one offers and which ones are BBB members.
These services are very tempting and show people receiving enough money to pay off bills, take a vacation... and they do pay... BUT if you are going to use one of these services there is one very important thing to keep in mind: They only pay you 10-20% of the meltdown value! Which is about 1/3 of the purchase price of the item. So a necklace that was worth $210 when purchased will have roughly $70 meltdown value... these companies will offer you $10-$14 for it. 5-7% of the purchase price.
You will be far better off with local jewelers, gold dealers or even pawn shops.