I found this one two weeks ago, but I thought it was worth sharing. Many times board games will only cost a dollar at yard sales, this one actually cost $1.50. After a while you will figure out which games are valuable and which are not, but I try to go with games that I have not heard of before. Also, any game with a dungeons & dragons theme, or a WW2 theme sells pretty well.
Sorry, you childhood copy of monopoly is worth about 50 cents, unless of course it was a first printing. The same is true for other common board games. I bought a pristine copy of Clue from the 1960's, it is worth $10, which is what it costs to ship anywhere. Stay away from common board games to resell unless it is a first printing in good condition.
Anyway, I picked up this game for $1.50 and it sold for $31. Board games are good to know about, because a lot of people will skip right over them. It was after noon in a large community garage sale when I found this. Hundreds of people had already passed it over.