Ask HN: Hacker News related sites?

There have been a couple of peripheral sites intended to provide features that HN doesn't provide itself. What are they?

Search YC

http://searchyc.com/

I use this, and a site-restricted Google search,

http://www.google.com/search?q=hacker+site%3Anews.ycombinato...

when I want to check if a cool link has already been posted here.