digg

Community helps to "surfaces" content.

StumbleUpon

Homepage is like a splashpage and not a dashboard. Has the "stumble" button.

Reddit

They call it social news.

Delicious

Has "stacks" concept and lots of tags.

BibSonomy

Has an interesting concepts webpage.

Licorize

Bookmarks into todo lists and presentations.

Below is a list of social network services.

Ning

social websites

Wall.fm

social network

SocialGO

social website

BuddyPress

social network

KickApps

on-demand social media application

GroupSite

Where Social Networking and Collaboration Meet