Ex Aliquo by Zerokyuuni
skyblock addon
ExNihilo (for 1.7.2) by Erasmus_Crowley
A mod designed specifically for skyblock maps
survival skyblock
Island Builder by LordDusk
This mod adds 1 CREATIVE ITEM only which you can sneak right click on any block you'd like. And it will spawn in an island for your needy friends.
skyblock