Delicious was either the first of one of the first social bookmarking sites. It has grown quite a bit and became popular with a lot of people in very short time. The service knows a lot of extensions and integrations into other services and sites. The simplicity made it what it is today.

Finally, after all these years, Delicious renews itself. I can only tell you what I have learned, as the preview is in private beta and I don't have an invitation :(. From what I have heard, the interface is quite different from the one we all know. But the real attentiograbber is the move to a new domain : the new Delicious will live on delicious.com. Techcrunch has cool screenshots of the new service, right here.

The preview is here, but you need an invitation to actually get inside.