Your best bet is to check with an antique dealer. It would only be worth something to a collector. Most people wouldn't be interested in it. Search online for a equine antique apprasier. You might find something there.
I have an old pony saddle hanging over the railing of my loft! Of course, I live in a log house, so it looks good there. I guess it might be out of place, depending on your decor.
Depending HOW old it is-if it's Civil War era, you might be able to sell it to one of the museums. I know in Gettysburg, there's all kinds of military memorabilia around. But I'm sure that even if it's newer (say, WWI or WWII era) it would still be worth something.
If nothing else, you could always look on ebay!
The average dog is a nicer person than the average person.