Look in the phone book for area auction houses. Call and find one that deals with the type of items you have and ask them how to go about getting them appraised and selling them. An auctioneer doesn't have the same conflict of interest that an individual dealer has. While he may want you to use his services for the sale, the selling price is determined by the bidders. He has no reason to lowball an appraisal to get you to sell him the item.
Charging a percentage of the value is actually a common way to pay an appraiser, though it never quite made sense to me. The more I tell you your item is worth, the more you have to pay me. Seems crooked, doesn't it?
There are online appraisal sites like this:
Antique Appraisals and Online Valuations Ranging From Furniture to Car Appraisals
I don't know much about them, but for only $9.95 it might be worth a shot.
The American Society of Appraisers and the International Society of Appraisers are the trade groups that you want to deal with. Make sure any appraiser belongs to one of those.
And yes, forget about any appraiser who, after giving you a value, then offers to buy the item from you.