Pew has been releasing pieces of their study, "Generations On Line 2009" for a while now, but for the first time that I know of they have released a large amount of data including this comprehensive chart of who does what on line.
Among other things, they have a comparison of broadband usage by age group comparing 2005 with 2008. As you can see the growth is huge.
Pew has also made available a number of charts including those included here in this slideshare presentation.
Much of this should be no surprise to you. But it is educational to re-familiarize yourself with where things stand.