Gossip Stone

Gossip Stones are found in Ocarina of Time, Majora's Mask, and Phantom Hourglass. These odd little devices do many a senseless thing. When you slash one with your sword it will tell you what time it is, or how much time you have left (that is, if you are playing Majora's Mask). If you place a bomb next to one it will shoot off like a rocket. You can also change the color of the stone this way, when the bomb changes to either blue or red, hit it with your sword. You can smash them into the ground using your Megaton Hammer. By using Din's Fire on one, the Stone will spin around and inexplicably stretch to double its height, soon snapping back to normal. After putting on the Mask of Truth, you will find out why they are called Gossip Stones. In Phantom Hourglass, they will talk to you without any conditions needing to be met. They might unlock certain challenges.

(It's important to note that the Gossip Stones in Phantom Hourglass have Wario's nose and moustache. Compare this to the fact that they tell you where treasure is in specific dungeons.)

What they say
Gossip Stones say alot of things in the games they are in. Sometimes it's helpful, sometimes it's just gossip.

Ocarina of Time
In front of the Temple of Time (Right to Left). After climbing up the vines at Hyrule Castle. On the Northwest side of the Deku Tree. Kokiri Village infront of the Lost Woods. In the Lost Woods past the Skull Mask Kid. Sacred Forest Meadow (Front to Back). Sacred Forest Meadow infront of the Forest Temple Infront of the Shadow Temple. Death Mountain while climbing to the peak. Death Mountain Crater entering from the peak. Lake Hylia near the Waterfall. Zora's Fountain close to the Zora's Domain entrance. Zora's Fountain infront of the Great Fairy's Fountain. Zora's Domain infront of King Zora. Zora's River near the entrance to the Zora's Domain. In various holes through out Hyrule. Zora River on the highest point. Hyrule Fields near Guerdo in a hole. Gerudo Valley lower Waterfall. Closer to Hyrule Castle. In a hole near a tree near Hyrule Castle. Near the Spirit Temple on the South side.
 * "They say that Malon set the original record in the obstacle course of Lon Lon Ranch."
 * "They say that Malon of Lon Lon Ranch hopes a knight in shining armor will come and sweep her off her feet someday."
 * ""They say that it is against the rules to use glasses at the Treasure Chest Shop in Hyrule Castle Town Market."
 * "They say that Gerudos sometimes come to Hyrule Castle Town to look for boyfriends."
 * "They say that if you get close to a butterfly while holding a Deku Stick in your hands, something good will happen."
 * "They say Kokiri are always followed by small fairies."
 * "They say that the small holes in the ground that you can find all over Hyrule make perfect breeding ground for bugs."
 * "They say that when non-fairy folken enter the Lost Woods they become monsters!"
 * "The owl named Kaepora Gaebora is the reincarnation of an ancient Sage."
 * "They say that strange owl, Kaepora Gaebora, may look big and heavy, but its character is rather light hearted."
 * "They say it's possible to find a total of 100 Gold Skulltulas through out Hyrule."
 * "They say there is a secret near a tree in Kakariko Village."
 * "They say that Biggoron's Sword is super sharp and will never break."
 * "They say Medigoron didn't really think about his own size, so his store is really cramped."
 * "They say that there is a secret road that leads to Lake Hylia."
 * "They say that there is a secret near the lone tree which is not far from the river in the north west part of Hyrule Field."
 * "They say that you can swim faster by continuously pressing B."
 * "They say that players who select the "HOLD" option for "Z TARGETING" are real "Zelda players!""
 * "They say Princess Zelda's nanny is actually one of the Shiekah, many though had died out."
 * "They say that the horse Ganondorf rides is a solid black Gerudo stallion."
 * "They say that there is a man who can always be found running around Hyrule Field."
 * "They say that there is a switch that you can only activate only by using the Spin Attack."
 * "They say that the thief named Nabooru, who haunts this area, is a Gerudo."
 * "They say that, contrary to her elegant image, Princess Zelda of Hyrule Castle is in fact a tomboy!"
 * "They say that you may find something new in a dungeons that you have already finished."
 * "They say that the treasure you can earn in the Gerudo's Training Ground is not as great as you would expect, given its difficulty."

Inside the Goron City in the Boulder Room.
 * "They say that there is a secret around the entrance to Gerudo Valley."

In the Manga
In the extra child chapters of the OoT manga, Link activates a Gossip Stone by hitting it, which reveals that Mido still wets his bed and that the Deku Tree is troubled that he cannot scratch his own back.

Majora's Mask
When attacked by Link's sword, the screen will shake and the stone will make a high-pitched noise. Then it will tell Link how many more hours there are until the Moon impacts. If you speak to it using the Mask of Truth, it will give you information regarding where to find other masks, or what you can use the other masks for (Example: "They say that the Couple's Mask has the power to silence arguments").