A few months ago I, full of ambition, started a series of posts about how the web is evolving, titled 'The Emerging Web', you can find them in my archives. I never got around finishing it. Basically the scope was a bit too broad. I started way back with how ARPANET became the Internet, and was planning to finish with all the current and exciting developments. There's enough material there to fill a book with.
What those developments of the contemporary web are is wonderfully explained in an article I couldn't have written in a million years.