LeoCAD

LeoCAD is a software program that provides users with a huge library of pieces similar to the Lego ones, which can be used in toy designing.
The interface of the application is intuitive, thus allowing any type of user to create their own 3D models. In order to enhance usability, aside from the usual menu bar, you are presented with shortcut buttons, a list of all the types of parts available, a preview pane, and a color panel.
The application is also highly customizable, seeing that you are able to toggle certain toolbars, split the window vertically or horizontally, set different types of keyboard commands, or change the preexisting ones, and so on.
LeoCAD is a powerful editor because, aside from enabling people to create specific toy designs, they can also use it in order to make building tutorials (for YouTube, Metacafe, Facebook etc.), and even animations.
In order to place bricks on the baseplate, all you have to do is drag them from the list provided on the right side of the main screen. Moreover, you should know that changing their positions is very simple, as the program displays different types of arrows which enable you to move it in all the ways you can think of. The application also lets you zoom in and out using the mouse scroll wheel.
LeoCAD has a library of more than 1000 different types of bricks, and importing external ones is another feature supported.
When the project is finished, you can see all the parts that you have used in it. This list is categorized by type of part and color.
All in all, LeoCAD is a very useful tool when it comes to creating objects from Lego-like bricks and animating them.