I've been working for a long time building terrain from bits and toys, using many of the techniques from Necromundicon and some of my own. Building things like this:
http://www.dakkadakka.com/dakkaforum/posts/list/608031.page
Recently I've decided to have another go my self at doing a of an in-progress how-to, sharing some of the techniques I've learned or created as shown on 3 projects from building through priming. Finished versions will be shown later.
The full tutorial with in progress pictures and construction tops is here:
http://chicagoskirmish.blogspot.com/2014/08/toy-bashing-urban-terrain.html
But here are some pics of the 3 projects within
A Power Station made from a Hot Wheels Launcher
Building under construction, made from a toy car parking garage.
Elevated Train Station from a Fisher Price toy.