Cubify Invent is a consumer 3D modeling software developed by 3D Systems. 3D systems states that this is their easiest tool for 3D creation and is designed from the ground up with 3D printing in mind. You don't have to be a professional CAD designer to use this software. 3D Systems has a series of video tutorials to help you learn the program.
Cubify Invent is available for Windows computers. The tutorials are available here.
The software download is available through the Cubify website for $49.00. There is also a 14-day trial available so you can try the software before you buy.