Adds various kinds of plants, fruit bushes, fallen trees, and a whole host of foliage and other ground cover.
Ethereal mod uses the v7 mapgen to add many new biomes to the world.
Adds a whole bunch of new types of trees, some bearing fruit or similar, using biome_lib for the placement engine.
A mod for Minetest to add underground realms.
Algae mapgen addition to "Minetest Game"
NodeCore Nature: Revised
Updated, fixed, enhanced edition of Winter94's NodeCore Nature
This combines several other mods that I consider a basic minimum starting point for worlds.
Gaël de Sailly
A map generator with valleys, rivers, mountains and many plants.
Grassy Goldenrod plant for Nodecore