hckr news - http://hckrnews.com/

Sortable HN - http://hnsort.com/

hnvue - http://www.hnvue.com/

HackemUp - http://www.mrspeaker.net/2011/04/11/hackernews-bookmarklet/

Search Y Combinator - http://searchyc.com/

WWHNS (What Would Hacker News Say) - https://github.com/marcua/wwhns/

HNSearch - http://www.hnsearch.com/

Visual Search - http://hnsearch.heroku.com/#h

Hacker News Resources - http://hnresources.com/

Kalimba - http://hn.embed.ly/

The Best of ... Hacker News - http://bitovod.com/hn/best-of

HackRSS - http://www.hackrss.com/

HN Trends - http://hntrends.jerodsanto.net/ ;)