The LWN security alert page
LWN currently maintains an archive of security alerts for the following distributions:
Caldera OpenLinux
Conectiva Linux
Debian GNU/Linux
EnGarde Secure Linux
Eridani Linux
Gentoo Linux
HP
Immunix
Mandrake Linux
OpenPKG
Progeny Linux
Red Hat Linux
Slackware
SuSE Linux
Trustix
Turbolinux
Yellow Dog Linux