I can see the potential for Del.icio.us. User-friendly access to library catalogues using it or similar social networking applications sounds like rhe way of the near future.

Exercise 7 RSS feeds

I found this to by fairly interesting, great for tuning in to your own particular interests. Unfortunately there were no feeds to some of my favourites, perhaps I shall try more later. I think these would be very useful to professional people, to keep up with news in their chosen fields.
Topix was good for latest news, just clicked on 'Top stories'. Ichecked out Syndic8 too, and Technorati. They all seem much alike, useful if you want to spend the time on them.