Bruce Sterling (one of the authors of the seminal steampunk novel The Difference Engine), has a new essay about the movement online. Well worth reading.
“Steampunk has become popular now because it is no longer just fiction. It is an international design and technology effort. Steampunk is a counterculture arts and crafts movement in a 21st century guise. […]
Steampunk’s key lessons are not about the past. They are about the instability and obsolescence of our own times.”
The essay is possibly the best examination I’ve ever read explaining the explosion in popularity of steampunk, and why it has widened beyond the historical-SF literature underpinnings.