Mixx. A new kind of Digg, and supposedly better. I have to say that I think most community link sites have a built-in problem because they scale badly. Not because of performance, but simply because of the angry herd they seem to attract once they reach huge membership levels. The prime example is Digg, which is, to my mind, has become a pretty poor resource recently. My preferred services (in no particular order):

• StumbleUpon. Superb idea, done elegantly. No superfluous nonsense, just great web recommendations based on an almost invisible bookmarking facility. Lovely.
• Reddit. Thoughtful, valuable link recommendation service which offers large community web wisdom without all the angry. The thinking man’s link community.
• Slashdot. Still solid, despite some rocky periods. A little bit angry, but becoming more valuable again because of the return of high quality informed comments from some serious people. This veteran geek place still rocks.
•  Metafilter. More of a gentlemen’s club than a link service, with a focus on higher quality posting ideals and conversation. Probably not quite as cerebral as they’d like to think, but a lovely resource for quality content nonetheless.
• Linkfilter. Small but interesting link site with a carefully moderated community who cross check posts with care and attention. A quaint little service, like a friendly cafe on a winter’s evening.
• Mixx? OK, I’m going to add it here more in hope than expectation. It’s early days, and although the content and community mix shows great potential, time will show whether the angry herd wrecks its promise.