In my opinion, creating a cental, free, cross-platform operating system lies in the very near future of the web. (That free part being optional actually but I like putting it in there.)
Take a look at these articles. Some are pretty old but they give a very nice view of the idea:
http://www.kottke.org/05/08/googleos-webos
http://www.kottke.org/04/04/google-operating-system
Will be putting the latest ones in as I find em.