I used this addon with blender 2.64 and working well.
I don’t think will be problems with the last version of blender: 2.66.
To using the Ivy addon, you need to activate this from user preference.
Search the addon “ivy” and check to activate this plugin. See image:
The next step is to add the ivy to mesh. Just press Shift+A keys and select the ivy.
The ivy will be created on cursor point. Select your mesh and point of ivy.
The next step is to make settings for ivy. This is my settings for the final result.
The ivy will be created with roots and leaves.
Also will need to set two materials for this.
This is the output :