This mod adds smooth motion to blocks that have different states (modes like open/closed, on/off). It is client-sided, so you only need to install it to the Minecraft client, and the animations will show for any block that has them. The blocks that have been animated are:

• Wooden/iron doors
  
• Trapdoors
  
• Fence gates
  
• Levers
  
• Repeaters
  
• Comparators
  
• Tripwire hooks

There are still some bugs to be worked out, but then it will be released. It will be a jar mod, and I doubt there's any way around that (without making it a whole lot more hacky, and therefore buggier).

This mod has pretty much been abandoned, until further notice.

Installation:

• Install Minecraft Forge
  
• Put the contents of the mod zip download inside minecraft.jar.