http://www.nsa.gov/selinux/ — Homepage for the NSA SELinux development team. Many resources are available in HTML and PDF formats. Although many of these links are not Red Hat Enterprise Linux specific, some concepts may apply.

http://fedora.redhat.com/docs/ — Homepage for the Fedora documentation project, which contains Fedora Core specific materials that may be more timely, since the release cycle is much shorter.

http://selinux.sourceforge.net — Homepage for the SELinux community.