As per the update from Security Focus. There are 18 million page views a month and 2.5 million unique users annually visiting this site. This clearly shows that this site is the preferred information source for security professionals around the world. Just type "security" in Google, This site comes in the top ten list.
I must say that this site is a heaven for people like me because of the valuable content it offers. There are many articles available which covers various topics like Penetration-Testing, Firewalls, Microsoft, Unix, Intrusion Detection (IDS), Virus and Incident Handling. They have a separate section called "columnist" where they offer knowledgeable issues that affect all members of the security community.
They have a huge Vulnerability Database which provides up-to-date information on vulnerabilities for all platforms and services. You can even search for vulnerabilities by using the CVE (Common Vulnerabilities and Exposures) number. Subscribe to the Vulnerability Database RSS feed to get the instant updates.
I'm currently subscribed to their mailing list. There are currently 31 mailing lists which allow members of the security community from around the world to discuss all manner of security issues. Please don't use your personal mail instead use a separate mail id for this mailing list. Also don't choose all the categories. Choose the one which best suites your interests.
My favourite section in this site is "Jobs". It's not like normal Job Websites. What makes this site unique is they only list Job openings which is related to Security. If you are looking for any Security related job post your Resume here. Also Employers can browse resumes to hire someone for their Job. You have to register before posting resume.
Do you have any Security related tool developed by you? you can submit your tool to Security Focus. They even accept your tools even if they are in Beta stage. I found many useful tools here. You can download the tools but this site will redirect you to the developers site to download the tool.
Visit Security Focus