Yes you can run vanilla minecraft very easily, but if you want extra features that are not available you would need to run a modded server, such as bukkit. The bukkit devs were recently hired by Mojang to create the standard minecraft build so it can handle these things right out of the box. Bukkit has literally thousands of plugins, from warps and teleports to economy to questing and npcs, strange mechanics and world editing features. Changing drops from blocks or mobs, giving you, or monsters more powers. Running multiple worlds at a time. The list is
here.