Bukkit

This plugin provides a complete set of commands to modify anything and everything about mob spawners and the spawned entities. It also allows for easy modification of the position where entities spawn, and the ability to copy and paste spawners.

This plugin is intended to be used by map creators, in order to provide a custom mob experience, but without the tedius work of switching between the game and MCEdit/another NBT editor.

• Change simple things like spawn rate.
  
• Or the entity spawned.
  
• Or where the entity spawns.
  
• Or what the entity is holding.
  
• Or specific properties for the entity (Creeper fuse time, wolf collar color, ect)
  
• Easily copy all the properties of a spawner, and apply those to a different one.
  

All from within the game. No exiting out to MCEdit or another NBT Editor, making your changes, uploading the new world, and restarting the server. Just nice simple commands, with instant results.

The list of commands is too large to list here, so the link below will to take you to a complete documentation on all that this plugin has to offer. Here are a few of the more basic ones.

• /spawner: Gives the player a mob spawner block.
  
• /tool [tool]: Gives the player the specified tool. (position/copy)
  
• /spawner entityid [entity]: Sets the spawner to spawn the given entity. A complete list can be found in the link below.
  

http://dmillerw.nodedevs.net/wordpress/mob-spawner-modification-plugin-documentation/