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 SELinux 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.