Wired Magazine characterized the recent boom (not bubble) that has emerged in Silicon Valley in an article titled The New Boom in the February 2006 issue. I think this quote describes the difference between a boom and a bubble nicely:
"Bubbles are inflated with hot air and speculation. They end with a wet pop, leaving behind messy splatters. Booms, on the other hand, tend to have strong foundations and gentle conclusions."
This table which was pulled from the Wired News article shows it more clearly and somewhat comically.
*Thanks to Niall Kennedy's Flickr account for the graphic from Wired Magazine.
