What other HN-like sites do you read?
resdirector: Metafilter and AskMetafilter.  They have a once-only $5 fee and a one-week waiting period before you can make your first post.  This filters out the Digg / Yahoo! Answers crowd.  They also have a culture of trusting users not to make "yo-mama" comments...which succeeds in keeping discussions cordial and intelligent.