Duplicate Special in Maya is a lot different from its cousin, Duplicate. Duplicate Special lets you duplicate objects, change the transformation attributes of the duplicated object(s), and duplicate mulitple objects at a time.
Create a cube to test the experiments on.
Duplicating Multiple Objects
Select your cube and go to edit>duplicate special... (open the options). Set the number of copies to 10. Hit duplicate special. This will create 10 cubes inside of each other.
What we want to do is duplicate 10 of them to stack on top of each other. Select a cube and go back to the duplicate special options.
Note: You can duplicate objects on any axis you choose. The Y axis is just used for an example. Use negative numbers for duplicating in the opposite direction.
Duplicating Objects In A Circle
Here's what we're trying to achieve:
First, select your object and go to the move tool. Hit insert on your keyboard and set the pivot point to the center of the grid (origin). It doesn't have to go there, but this is the point at which Maya will rotate the objects around.
With the object selected, open up the duplicate special options. There will be 20 objects all together. There will be 19 objects duplicated, because the first object is counted. So set the number of copies to 19.
That worked. Let's explain how we arrived at the 18 degrees that we needed to duplicate each object.
Mirroring A Duplicated Object
Select a model and open the duplicate special options. Set the scale on the X axis to -1.0000. now hit duplicate.
Continue using the duplicate special options with different settings to be able to see the cool effects that can be created with this tool. I didn't cover half of them here.