If I'm being honest, my favorite part of Minecraft isn't the mining or the crafting or the building or the rampant chicken-punching. Instead, my truest joy is simply wandering around an ever-expanding world, taking in the often awe-inspiring sights and sounds of blocky nature. One day, I will venture to New Zealand and go on a trek for the ages. Until then, I have Minecraft. But after a while, even those procedurally generated delights start to lose their luster. Enter the brand new "Biomes O' Plenty" mod. It adds just about every geographic configuration you could possibly imagine - short of outer space and the inside of David Bowie's mind. Details after the break.
Biomes O' Plenty adds a whopping 33 new environment templates to Minecraft, ranging from cherry blossom groves to murky marshes to dusty red mesas to ominous woods to what I'm pretty sure is actually just Proteus. There's a full gallery of every last one with descriptions here.
You also get 14 new object types (including lots of dirt, mud, and dead plant - for that authentic post-apocalyptic feel) and a few new crafting/smelting recipes. A word of warning, however: this one's not compatible with other biome mods, and attempting to alter it yourself is inadvisable.
Still though, it's really quite a package. And as Jim recently pointed out, PC games are all about terrain. Jim only speaks in absolute truths (and the occasional wisdom-bestowing riddle), so you can trust him on that. At any rate, give Biomes O' Plenty a try for yourself here.