http://www.bukkit.fr/index.php/topic/13063-commandlater-planifiez-vos-commandes/

CommandLater.java

package fr.neatmonster.commandlater;

import org.bukkit.Bukkit;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.scheduler.BukkitRunnable;

public class CommandLater extends JavaPlugin {
    public static class CommandRunnable extends BukkitRunnable {
        private final String command;

        public CommandRunnable(final String command) {
            this.command = command;
        }

        @Override
        public void run() {
            Bukkit.dispatchCommand(Bukkit.getConsoleSender(), command);
        }
    }

    @Override
    public void onEnable() {
        for (final String path : getConfig().getKeys(false))
            try {
                final long time = Long.valueOf(path);
                if (getConfig().isString(path) && System.currentTimeMillis() < time)
                    new CommandRunnable(getConfig().getString(path)).runTaskLater(this,
                            (time - System.currentTimeMillis()) / 50L);
            } catch (final NumberFormatException e) {}
    }

    @Override
    public void onDisable() {
        getServer().getScheduler().cancelTasks(this);
    }
}

plugin.yml

name: CommandLater
version: 1.0
author: NeatMonster
main: fr.neatmonster.commandlater.CommandLater