For anyone involved in web projects it's interesting to follow the development of services that are really raising the bar of what has been done before. I believe there are two interesting areas to follow right now; Web Office and Application Creation.
As a coincidence two different blogs today have put together overview of those.
Web Office
Those are the ones aiming to (in the long run) compete with Microsoft Office, for example Googles Docs & Spreadsheet and ZoHo. The Read and Write blog has a great overview in this post.
Application creation
Not an application itself, rather a platform to build your own application without programming skills. Read more about it this post by the Techcrunch blog.