Thoof
Gosh. This is so simple, so obvious; should’ve existed for years. But somehow it took Ian Clarke plus several friends to conceive and implement it.
They’re still changing things around, so expect Thoof to go poof every once in a while. They don’t have subsections like Digg’s ‘gaming’ or Reddit’s ‘programming’, but attempt to customize the stories shown on a per-user basis, so it’ll be interesting to see how it scales when/if it takes off and gains more users.