Perhaps the client-side piece of the puzzle can be solved by simple Live CDs that are built primarily or exclusively for web browsing. One such Live CD is cl33n (http://cl33n.com/). cl33n just boots, connects to the internet and opens Firefox. There is no other functionality.
I put cl33n together after running a bunch of usability experiments existing live CDs and occasional computer users. I loved all the live CDs that I tried and I thought they would work out great but unfortunately the users (all Windows beginners) were confused by each of them.