Nanopunk refers to an emerging genre of speculative science fiction still very much in its infancy in comparison to other genres like that of Cyberpunk.
The genre is similar to biopunk, but describes the world where the use of biotechnologies are limited or prohibited, so only nanotechnologies in wide use (while in biopunk, bio and nanotechnologies often coexist).
Currently the genre is more concerned with the artistic and physiological impact of nanotechnology, than of aspects of the technology itself which is still in its infancy. Unlike the Cyberpunk, a low-life yet technologically advanced character, the personification of a Nanopunk can be set 'hard' or 'soft', depending on your views of the impact Nanotechnology will have on our future.
Kathleen Ann Goonan (Queen City Jazz) and Linda Nagata were some of the earliest writers to feature nanotech as the primary element in their work.
Linda Nagata's Tech Heaven is a futuristic thriller about Katie, a woman whose husband is about to die of injuries sustained in a helicopter crash. Instead of dying, he gets his body cryogenically preserved so that he can be reawakened when med-tech is advanced enough to heal him.
Another famous example of this genre is Neal Stephenson's "The Diamond Age". Some novels of Stanislaw Lem, including Weapon System of the Twenty First Century or The Upside-down Evolution, The Invincible and Peace on Earth could also be considered precursors of nanopunk.