i've still not found one
what difficulty do you play on? how'd you find it? what was it like?
It dose not matter what difficulty you play on, Go in tunnels. Like automaticly generated tunnels. If you find Cobblestone or odd looking cobblestone (Mossy Cobblestone in this case) that you never planted it is likely a dungeon. Break a hole into the dungeon and destroy the Mob Spawner, these usualy spawn Zombies, Spiders, Creepers, or skeletons, (Slimes are not avaible as a Mob Spawner). When you break the spawn go to the 1 or 2 chests in the room. That usualy contain loot that you might find usefull. Such as a saddle (for riding pigs), String, Buckets, Wheat, Apples, Records (Very Rare), Iron Bars, and a couple more items I cannot remember. Since MossyCobblestone is not found elsewhere on the map you might aswell stock up on it. I use the empty dungeon as a base underground incase I cant get to my house. If you find a Dungeon set the mode to "Peacefull" so if it is a creeper spawner you wont loose the loot in the case. Cause Creepers and blow it up including you. If you somehow obtain the Mob Spawner put it neer your house. Do not put it in a enclosed area, or else the mobs wont spawn (Due to the abuse of Mob Spawers with Automatic Kill n' Item Catch machines). Instead put it outside. And you got FREE piggys! Which can supply you with pork.