Microsoft Security Website

http://www.microsoft.com/security/default.mspx

Cyber Security Alerts

US-CERT

United States Computer Emergency Readiness Team

Cyber Security Alerts provide timely information about current security issues, vulnerabilities, and exploits. They outline the steps and actions that non-technical home and corporate computer users can take to protect themselves from attack

http://www.us-cert.gov/cas/alerts/

Websense

Websense Security Alerts provide hundreds of organizations around the world with the latest security warnings on malicious Internet events including spyware, phishing, spam, crimeware and compromised Web sites.
 

http://securitylabs.websense.com/content/alerts.aspx