Ever saw a really awesome plugin, and thought "Wow, I'd really love to have that as a mod for singleplayer!" WELL YOU CAN! Here's how: Download the Bukkit server and save it into a folder on your desktop. Run the server. Download any plugins you want and put them in the "plugins" folder. In the server properties file, set the IP to 127.0.0.1 Start Minecraft and go to Multiplayer. Type "localhost" as the server IP. Enjoy! You'll experience NO lag, and other players cannot join your server. It is the same as playing Singleplayer, except you can have all the plugins you want!