Thoughtful House (in Austin, TX) just released updated data for 2008-2009. You can access graphs for all of the states and outlying areas here.
This data is based upon reports of students receiving special education services due to a diagnosis of autism.
Please keep in mind that these shocking increases do not include students who are home schooled, in private placements, too high functioning to receive special education services, or not receiving the services they need at all.
The most significant note was 1 in 67 eight-year-olds receiving special ed. services for autism in the state of Minnesota. I have heard that Minnesota is a leader in terms of providing appropriate services for our kids, so if you consider that even this number is likely underrepresented, well, we should all be completely appalled.
I cannot tell you how many families I know in the state of California whose children seem to clearly be impaired by autism and yet are told that they do not qualify for services under that label. (or any other label for that matter, unfortunately) So consider just how high the numbers might really be in your state.