California had 7 cities rank in the top 20 for the fastest growing cities (by percentage) from 2004 to 2005. According to the US Census bureau, Elk Grove (near Sacramento) was #1. Other California cities in the Top 20 were Moreno Valley, Rancho Cucamonga, Miramar, Irvine, Bakersfield, Lancaster, and Visalia.
A PDF chart of the Top 25 can be found here.
There are some other charts you might find interesting: