OWASP

List of cheat sheets:

• PacketLife: http://packetlife.net/library/cheat-sheets/
• OWASP: https://www.owasp.org/index.php/Cheat_Sheets#tab=Main

Free eBook: OWASP Top 10 for .NET developers:

http://www.troyhunt.com/2011/12/free-ebook-owasp-top-10-for-net.html