General

• OWASP
  The Open Web Application Security Project - free, professional-quality, open-source documentation, tools, and standards.
• WASC
  Web Application Security Consortium
• Real World Web Hacking URLs
  A list of news sources on real-world websites' hacks
• SANS
  Information and Computer Security Resources
• cgisecurity
  A good collection of web security related papers
• Threats and Countermeasures
  Threats and Countermeasures Community knowledge base

Related Papers

• Web Application Security
  Web application vulnerabilities, security testing and assessment
• Program Analysis
  Static and dynamic analysis papers