A new mod for the PC version of Minecraft adds 30 unique biomes for players to choose from, according the mod's thread on the Minecraft forums.
The "Biomes 'O Plenty" mod can be installed but not altered, with biomes generating at random. Players can choose from a dozen new blocks to build with, including Mud, Red Rock, Ash, Dead Grass, Wildflower, and Willow blocks. Creator TDWP_FTW also developed the "ExtraBiomes XL" mod, and has included a small sampling from his previous mod in the biomes pack.
Biomes include bogs, crags, deadlands, glaciers, tundras, and more fantastical environments like the Ominous Forest and Shrubland. The mod is also not compatible with other mods that change the game's biome, and can only run with the ModBuilder program.
"Biomes 'O Plenty" can be downloaded off the Minecraft forums.