Provided by the US Government, this site provides weekly summaries of security issues and new vulnerabilities for various operating systems. This site also provides patches, workarounds, and other actions to help mitigate risk.

They study internet security vulnerabilities, provide incident response services to sites that have been the victims of attack, publish a variety of security alerts, and research security and survivability in wide-area-networked computing.

Brings together a variety of computer security incident response teams from government, commercial, and academic organizations. FIRST aims to foster cooperation and coordination in incident prevention, to prompt rapid reaction to incidents, and to promote incident prevention programs.

Their site states that they are "A non-profit association of computer security professionals who have a common goal of improving the understanding, theory, and practice of computer security. To this end, ACSA supports a number of activities, all of which serve the goal of improving the computer security field."

Computer Incident Advisory Capability computer security bulletin listing.

NTBugtraq is a mailing list for the discussion of security exploits and security bugs in Windows NT, Windows 2000, and Windows XP plus related applications.

Lists places you can get on email lists to receive security bulletins for Linux.

Lists security bulletins with Sun brand UNIX computers.