Even if they've never been used if they're 20 years old they're prolly not worth a whole lot what with all the advances in technology. As the poster above mentioned, check out ebay and see if anyone else is selling a similar set that you could use as a price gauge. If they are newer they could be worth many hundreds. Here's a link to an ebay search for Taylor Made:
http://sporting-goods.search.ebay.com/taylor-made_Golf_W0QQcatrefZC12QQfsooZ1QQfsopZ1QQsacatZ1513As far as the balls go alot depends on the brand and the condition. I am assuming that they are used and probably of various types, probably used for practice but without seeing them I can't tell you much more than that. If they are used and scuffed they are probably not worth more than $10 or $20.
Another idea, check out this Golfsmith page:
http://www.golfsmith.com/po/on the right hand side they have "grade your clubs" link to see how much used clubs are worth in trade in, they may just buy as well, if there's a store near you.
There's also a chain of stores called "2nd Swing Golf" that sells only used equipment and purchases them too:
http://www.2ndswing.com/ as well as another chain that buys and sells used sports equipment of all sorts, "Play It Again Sports."
http://www.playitagainsports.com/playitagainsports/myheadline.asp?S=7312&P=3979&PubID=4332DON'T sell at a garage sale. If none of those stores are near you, take the clubs to a few different golf stores and pro shops and see what they can tell you about them and see if they're interested in purchasing.
on edit: take the golf balls to these stores too, they'll be able to tell you what they're worth. The clubs, if new and of a good model very well could bring many hundreds.