AutoDesk 123D is free and works very well. I use it alongside the more expensive AutoDesk products (Inventor & AutoCAD).

SketchUp is also free and works well.

Depending on budget though you may want to look at Solidworks (supposed to be the best for 3D design, I've yet to try it), 3D Studio Max, AutoCAD (full version not LT).

After I made this thread I went on solid works to see if it is nice but there are many different programs and I do not know which one to use

If you have never done any 3D work before start with AutoDesk 123D, get a feel for what you need to do. Once you need to refine your designs, add details etc. then opt for something better.

I use AutoCAD 123D design. they have multiple software for 3d design though.

Openscad can also be useful for 3d modeling. It uses a parametric model. Using it is more like programming. It allows importing if meshes (stl) and dxf files for 3d extruding. I have found it useful for modifying existing stl mesh files or using stls to modify my own designs. It is a bit awkward to use, but it is free. If you like GUIs it is not what you are looking for.

i just downloaded 123D design i will see how it goes and let you know

I just remembered watching a video of nick and jermie they were designing something to replace the Bluetooth module I will try and get a link

Does anyone know what program he might have used to help jermie design the module that was suppose to connect to the arduino