Are they good/special cards, or just common cards? If they are good cards (worth some money), you could post them with pictures on ebay or craigslist. Also, if they are good, you could try trading them in to a card store.
We had a garage sale a couple weekends ago and my son sold pokemon and yu-gi-oh cards. He sold bundles of 50 common pokemon cards for $0.75 and $1 (rubber banded, in a stapled shut ziplock). He sold his good yu-gi-oh cards for $1.50-2.50 each. He had a nice set of yu-gi-oh cards in a gold case that he sold for $10. He was not ready to give up his good pokemon cards yet..
Good luck!