Delicious

I have been using delicious for a while, and for me it has been one of the most useful web 2.0 tools. If you move around the libraries using different desks, you don't have to save your favourites on each computer - they are all together in one place. I also use it to park useful websites I discover while doing reference queries. Tagging them then makes it easy to find all saved sites on a similar topic.

I like the fact that you can have private and public bookmarks. I have made sites like online banking private, and they are then easily accessible when you are travelling, for example.

I had a look at Digg - didn't do much for me, so I haven't signed up.