AutoDesk 123D Make
123D Make is slicing software often used in conjunction with a laser cutter or CNC router instead of a 3d printer. This program allows you to slice a digital 3d model into layers of any thickness you choose, with the intent of then stacking those layers in order to create a large 3d model out of materials such as cardboard or plywood. It can also be used to create complicated 3d models which can be assembled like puzzles.
123D Make is free software provided through the AutoDesk 123D collection, anyone can download and install it for free on their personal computer.
UPDATE 3/21 123D Make will cease to exist on March 31st, 2017. However, the program can still be accessed through AutoDesk Fusion 360 by installing the new app as an option in the program. Follow these instructions to install and use the slicer in Fusion 360.
Install Link: http://www.123dapp.com/make
Note: the Autodesk 123D series of programs is being phased out in early 2017. All of the features of 123D Make have been implemented into AutoDesk Fusion 360.