Finding data on accessing and use of the internet is very difficult. However tables recently released from the US Census Bureau's Current Population Survey (CPS) School Enrollment and Internet
 Use Supplement do provide some insights.
The tables display national and state level data and 
examine householder and individual characteristics by school enrollment,
 age, race, sex and Hispanic origin. Additional tables use data from the
 Survey of Income and Program Participation (SIPP) to examine how and 
why people connect to the Internet. The CPS has been collecting data on 
computers and Internet use periodically since 1984. SIPP data on this 
subject have been collected since 1998.
These data tables appear on the  US Census Computer and Internet Use page.
