ExtraBiomesXL – New Biomes and Items!
This is personally one of my favorite mods, it adds a whole new aspect to the game with realistic and diverse biomes. I wish some of these biomes would be introduced in the official minecraft version as it out does some of the current ones in creativity and uniqueness.
Official Thread: http://full.sc/JCgItk
"ExtraBiomesXL isn't designed to overpower Minecraft or severely alter gameplay, but instead to add new aesthetic blocks and items that greatly enhance Minecraft's landscapes and exploration, without being invasive (although you should beware the quicksand!)."