Seems like there should be an "Antiques Internet Show", or something like that. About.com has an advice page, with tips. There is a site below, I am sure you will pay there. For Paintings you use Artprice.com, but it costs. Most antiques are in a category, and there are sites for many of the possible categories. I usually just compare an item to something someone else is selling. This seems like a Void that needs to be filled.
References :
http://antiques.about.com/od/valuationtips/Tips_for_Valuations_of_Antiques_Collectibles.htm
http://www.glamorganantiques.co.uk/appraisal.htm
http://www.web.artprice.com/start.aspx Art Prices

http://search.yahoo.com/search?p=get+valuation+for+antiques&btn=Search&tab=Web&ei=UTF-8&pstart=1&fr=my-vert-web-top&b=11