I recently been playing around more and more with 3D modelling.
There are two reasons for this.
Firstly as you may have seen from my previous posts I am building a 3D printer. Secondly I have been prototyping different computer game ideas in Unity for a while now and decided to switch to 3D for some of my ideas.
Here is a couple of images of a tank model I am working on. It does not really have a dedicated purpose yet but I thought if I made any models for use in games they could be simplified for printing purposes.
The weapon of choice for my 3D modelling is Blender. This is because it is a free open source application with plenty of tutorials on itself and integration with Unity.
It looks like 3D printing will pose its own challenges where things like over hanging parts will be a challenge. This does give me the idea of printing a model over several runs in kit form though which would be cool.
Shane's Shed 
Blender is a powerful program but I found it difficult to figure out. I use and LOVE Cubify Design which is only $200 away from being free, but there are many other completely free 3d modeling programs out there.
Before you hone your skills too much with one program you might be interested in checking out this awesome thread on Thingiverse: “What is the best FREE 3D modeling software for serious use?”
http://www.thingiverse.com/groups/engineering/topic:66
Thanks that looks like a good read. I don’t mind spending a bit on a design tool if it’s nicer to use. The 3d printer build has an Autodesk 123 with it so I might give that one a go as well.