Hacker News Stack - Focus on the really fresh and unread news in Hacker News.
The Y Combinator Database - The definitive database of YC companies with all the metrics
Box Piper Hacker News - Re-Imagined Hacker News for this decade.
Startup School - How to start a startup, by Y Combinator
Hacker News Front Page Explorer - A database of top ranking Hacker News front page posts
Y Combinator Companies - Interactive list of all 1000+ YC companies