Hey Yesterday I found a double Zombie Spawner. I even build it into a Grinder. So you basically stand there and kill zombies from 2 different Spawners! So this is Twice as efficient as a normal Zombie Grinder! The Spawner is Located at the Wasteland of SMP1 It's within 500 blocks of Spawn so you dont need to walk that much to it. I will sell it for 7.500r Dont forget to read THIS before BUYING the Spawner http://empireminecraft.com/threads/guide-selling-mob-spawner-locations.9738/
To anyone interested in buying, be sure to this thread: http://empireminecraft.com/threads/guide-selling-mob-spawner-locations.9738/ Sellers are supposed to include a link to it in the post, so make sure you read it too, hYLiF3.
Erm... i dont think anyone would want to buy it when it is located in the wastelands. Since it can be reset.