When I find the time (rare), I've been working on a 3D project of my own. The above is the completed low-poly mesh for a transforming bike design. It's been carefully 'engineered' with no 'cheating' e.g. parts that shrink or overlap each other when transformed.
The scenario for the design involves a human pilot, who occupies roughly1/3 of the height of the robot internally - it's not a sentient, Optimus Prime-style robot. Again, the cockpit has been taken into account. In line with the 'real world' design, the transformation has also been kept as simple and robust as possible, avoiding the kind of complex, delicate transformations of typical high-end models. This is helped by it not having to turn into a perfect recreation of e.g. a Porsche 911. I'm more of a Macross fan than a Tranformers one, though both are cool.
The next step is to detail it up, possibly in Mudbox, texture it, and finally add a rig capable of handling the transformation. I then intend to render a short sequence that shows the moving vehicle transforming into robot form. So not much work there, then.