This is good news. According to a new report from the Solar Energy Industries Association (PDF):
The United States is on track to experience a record year for PV installations in 2010. In the first half of the year 339 MW of grid-connected PV were installed. On an annual basis, this represents 55% growth over the 435 MW installed in 2009. Many factors contributed to this growth, including a drastic decline in 2009 module prices, continued federal support from the Section 1603 Treasury Cash Grant in Lieu of Investment Tax Credit program, and expanding state-level targets for solar power. (PDF)
On the map above, you can see that California and New Jersey are leading the way. To put those circles in perspective, 120 megawatts—roughly the amount installed in California—is enough energy to power 60,000 homes.
Also, it's important to note that this isn't all the solar power installed last year. It's just the solar photovoltaic panels. There are also concentrated solar plants and solar heating systems and solar pool heating systems and so on. The estimated total solar power capacity installed in 2010 is 1 gigawatt, enough to power half a million homes.