Bukkit

The multiworld plugin made by ferrybig

Creates cleanroom-style flat world generator with fully customizable layers. It can also be used to create empty space maps!

Pre-generates chunks, quickly, efficiently, and safely

PlotSquared

A Skyblock Plugin

Nothing but void!

This plugin allow full control of normal world generator

Exotic Garden

Provides automated plots with protection (MultiWorld support)

An epic Minecraft Bukkit world generator

IslandWorld - Survive on small isle

Its a plugin, but its mod-like: New mechanics, new worlds, custom bows and strucutres, faster game, survival reinvented.

A simple void world generator.

Multi-worlds for your server

CityWorld

A plugin for Bukkit based Minecraft server that adds a floating island dimension similar to the old skylands.

An Automated Hunger Games plugin!

Floating island based world generation

Giant Caves is a bukkit mod that creates giant underground caves in the world.

uSkyBlock