In a land far away, a kingdom was famed for its wine. In one month, the king was scheduled to throw a huge banquet in honor of his birthday. Unfortunately, the king had many enemies. One day, about a month prior to the banquet, he went down to the wine cellar and found a spy poisoning one of the wine bottles. Unfortunately, the king did not notice which of the bottles was poisoned. The spy was interrogated and questioned, but refused to answer. He said that since they didn't know which bottle was poisoned, they were all rendered useless. Since they couldn't get anything out of him, they killed the spy for his treachery. Before he died, however, the spy did tell them a few things about this particular poison:

1.) The poison is so strong that any amount of dilution will have no effect on it, so if they tried to dilute the wines, it would still be poisonous.
2.) The poison would take 1 month to work. Only if after 1 month someone dies, then you know he was poisoned.

This made the king very upset. Three brave men came forward and said they would sacrifice their lives to honor the king.

In short:
You have 8 wine bottles, 1 month, and 3 expendable men. Since you have 1 month, you only have one shot at this. At the end of the month, you have to know EXACTLY (without guessing) which wine bottle is poisoned and what other 7 are good. Obviously this will require arranging the 3 men to drink the bottles in a certain fashion.