A user on the American Marketing Association E-commerce/Internet Marketing Shared Interest Group asked the following question today - I thought the list of resources generated as a result of the question might of benefit to all...

I'm interested in websites which provide basic demographic info on internet usage. For example, % of U.S. citizens 55+ by state who use the internet for information and email communication.

Related Resources:

CyberAtlas is always my first stop for stats
http://cyberatlas.internet.com/

WebReference has a list of more sites that offer free or paid stats services
http://webreference.com/internet/statistics.html

Check out their press section at Mediamark for more info on their reports
http://www.mediamark.com/

Pew Internet Project reports are based on thier research, surveys, and analysis
http://www.pewinternet.org/reports/

Also, you may find that 'googling' a series of the keywords in your question below yield additional helpful results such as the following:

http://www.seniorjournal.com/NEWS/Features/05-25-1InetUseby55-64.htm

http://www.virtualgiving.com/papers/Seniors.pdf

http://www.nua.ie/surveys/index.cgi?f=FS&cat_id=31

If anyone knows of more, please put them in the comments. Thanks!