It's all scattered, so I thought this would be useful for others applying:
http://ycombinator.com/howtoapply.html
http://www.giftrocket.com/blog/yc-application-checklist
http://dl.dropbox.com/u/27532820/app.html
http://valleybot.com/blog/2011/10/2/deconstructing-a-successful-yc-application.html
http://news.ycombinator.com/item?id=855057 --> http://scotchi.posterous.com/
YC application tips- collection of links | Heykuki News