The prophecies usually go like this: A big evil is plaguing the land. Only one person (usually a man) has the power to vanquish this evil, and will rise up at the exact moment when the world needs him most. He will be near indestructible and the land will enter a golden age of prosperity as a result of this.
The result of this is that the evil entity attempts to somehow kill the prophecised person while they are still a child, which means that they somehow get away (as they tend to do, they're slippery things). Then they are raised by good honest folk and are completely oblivious to their destiny. Eventually something comes along that means their destiny is revealed (usually the death of their guardians) and they usually revoke it. This usually ends with the hero eventually embracing this prophecy (while at the same time not following it) and fulfilling his destiny.
A couple of different stories spring to mind with this: Star Wars, Harry Potter and The Sword of Truth to name a few. The same basic concept is overlaid in all these, despite their different plot and characters, but the prophecy drives them all in the same direction. I think the prophecy idea in fantasy can be overdone, though, and it may get to the point where the stories become stale. There's a great short story over at PodCastle by Tim Pratt called Another End of the Empire. Here, the evil overlord hears such a prophecy, and knows exactly what will happen if he takes the standard measures, and so takes a very radical approach (I highly recommend it).
What do you think? Am I right in thinking that this prophecy idea is overdone? Can you think of any other fantasy stories that have the same thing? Any that use prophecy in a different way?