@stake Advisories: http://www.atstake.com/research/advisories/index.html
CERT Advisories: http://www.cert.org/advisories/
Check Point's Knowledge Base: http://support.checkpoint.com/
Check Point's News Server: news://nntp.checkpoint.com
Common Vulnerabilities and Exposures Database: http://cve.mitre.org/
DNS Resource Directory: http://www.dns.net/dnsrd/
Firewall Wizards Mailing List: http://honor.trusecure.com/mailman/listinfo/firewall-wizards (not specific to FireWall-1)
FireWall-1 FAQ Page: http://www.phoneboy.com
FireWall-1 Mailing List: http://www.checkpoint.com/services/mailing.html (searchable indexes at http://msgs.securepoint.com/fw1/)
FireWall-1 Gurus Mailing List: http://www.phoneboy.com/gurus
Firewalls Mailing list: http://www.isc.org/services/public/lists/firewalls.html (not specific to FireWall-1)
Internet Firewalls FAQ: http://www.ranum.com/pubs/fwfaq/
Internet Security Servers Security Center: http://xforce.iss.net
Lance Spitzner's Publications: http://www.spitzner.net/ (contains various topics, including using snoop, configuring your NICs, hardening Solaris, and stuff on Honeypots)
NTBugtraq: http://www.ntbugtraq.com/ (Windows Security site)
ntsecurity.nu: http://www.ntsecurity.nu/ (Windows NT and 2000 Security site)
SANS Institute: http://www.sans.org/ (security education, research, and training)