When I was a kid, there always seemed to be someone in the neighborhood building some wonderfully absurd kit car on an old VW chassis. That basic VW platform was the basis for so many DIY car projects. Sadly, there's nothing like that now. But maybe a new open-souce car called the Tabby will change that.
I really love the idea of a viable open-source car platform: something that's cheap, relatively easy to build in a normal backyard or garage, and actually usable when completed. The old Beetle chassis/drivetrain combo is a pretty hard standard to beat, and it's still my benchmark for future DIY car platforms. You could find them anywhere, it contained pretty much everything you needed (suspension, transmission, electricals, seat mounting, body hard points, etc), it was cheap, and the end result of your home-built project, whether it looked like a vintage MG or a really tiny big rig, was something you could register and drive on the road.