I came across an interesting software recently – eyeOS, which is meant to provide a desktop like environment on the web. It provides you with an entire desktop like interface on the web with some basic office applications like calendar, calculator etc. In case you want to try it out, you have to create a new account (quite a simple process) on the site, and then log in to try it out. You can also customise the desktop theme and install new applications (not sure what’s available for it though).
I was also checking out the eyeOS site, and it is apparently an open source project. It is also possible to download and install eyeOS on your system. The Windows package comes with its own web server and browser (based on Apache & Firefox respectively), and so you do not require any kind of additional setup. There is also a FreeBSD package and the source available for download. So, if you want to experiment with it, check it out on the eyeOS download page.