A recent article in Technology Review describes a way to make multi-layer carbon nanotube circuits.
Nanotubes are better than silicon transistors, but are hard to use. This approach includes several techniques:
1) Grow the nanotubes on a separate substrate, then stamp them onto the circuit. This lets the circuit stay at low temperatures.
2) Use a strong voltage pulse to "burn out" unwanted nanotubes. (I read of this idea years ago, but I guess it's more practical now, or something.)
3) Stack multiple layers of nanotubes, to make a more complex circuit.
Common definitions of nanotechnology include bulk imprecise materials (like computer chip silicon) as long as they are manufactured with sufficiently small patterns. Thus, computer chips have included nanotechnology for a decade or so already; conveniently, semiconductor research was approaching the (definitional) nanoscale right as the definition was formulated.
By contrast, nanotubes are single, precise molecules being assembled to build up useful larger systems. This is a lot closer to the original meaning of the word.
At any rate, with several ways now known to combine nanotubes into circuits, it seems likely that nanotube circuits will be researched pretty intensively; this means that research dollars will go into better ways of making and characterizing and handling nanotubes, as well as better ways of building and characterizing nanoscale structures in general (including DNA structures). There's a lot of money in computer chips, and a lot of incentive to develop new ways of making them. So this should give a significant boost to precise nanoscale structure technologies.