On the left: A truck made with the #8421 mobile crane set and parts of the Mindstorms kit. More pictures are here.
On the right: An automatic level crossing. A video can be found here.

On the left: A rack and pinion steering car made with the #8421, set, the 3804 set and the 3800 set.
More pictures are here and click here for a video.
On the right: A motorized version of the mobie crane set (only the top of it). More pictures are here.