The download is for the normal version of the map, if you want more of a challenge then try the hardcore version.
NOTE: The download for this map goes to the official SkyBlock site (skyblock.net). (CURRENTLY DOWN, USING BACKUP LINK)
Map Info:SkyBlock is one of the most popular minecraft maps ever created. The concept behind the map is very simple; you spawn on a floating island and must survive and complete challenges with the resources available to you.
This map was the original floating island type survival map, and a vast majority of survival maps are based on it.
Note: If you die before sleeping in a bed, it may be impossible to spawn back on the island.
If you would like more information about this map, or wish to contact the creator, then please visit the map's official website, located here: SkyBlock.
Rules: Do not purposely jump off the island to regenerate your health. Do not make a bridge to the mainland. Play on at least easy difficulty.
Challenges: 1) Build a Cobble Stone generator. 2) Build a house. 3) Expand the island. 4) Make a melon farm. 5) Make a pumpkin farm. 6) Make a reed/sugarcane farm. 7) Make a wheat farm. 8) Make a giant red mushroom. 9) Craft a bed. 10) Make 64 stone brick's. 11) Make 20 torches. 12) Make an infinite water source. 13) Craft a furnace. 14) Make a small lake. 15) Build a platform 24 blocks away from the island, for mobs to spawn. 16) Make 10 cactus green dye. 17) Make 10 mushroom stew. 18) Craft 10 Jack 'o' lanterns. 19) Craft 10 bookcases. (As of Minecraft 1.3, crafting bookcases is only possible if cows spawn on your island) 20) Make 10 bread. 21) Collect 10 Ender-pearls. 22) Cook 10 fish. 23) Craft 10 Black Wool. 24) Craft 10 Gray Wool. 25) Craft 10 Light Gray Wool. 26) Craft 10 Lime Green Wool. 27) Craft 10 Red Wool. 28) Craft 10 Yellow Wool. 29) Craft 10 Pink Wool. 30) Craft 10 Green Wool. 31) Craft 10 Orange Wool. 32) Craft 10 Snow Golems. 33) Craft 20 Paintings. 34) Build and light a nether portal. 35) Craft 5 Gold Ingots. 36) Craft 16 Glass Panes. 37) Collect 50 birch logs. 38) Collect 64 arrows and craft a bow. 39) Craft 10 stone buttons. 40) Craft 30 stone slabs. 41) Craft 10 signs. 42) Craft 20 ladders. 43) Craft 20 fences. 44) Craft 20 fence gates. 45) Craft 10 levers. 46) Craft 10 trapdoors. 47) Craft 10 stone pressure plates. 48) Craft 10 wooden pressure plates. 49) Collect 64 bonemeal. 50) Craft 20 cobblestone stairs.