Authoritive Bodies
IANA - Internet Assigned Numbers Authority
ICANN - Internet Corporation for Assigned Names and Numbers
NRO - Number Resource Organisation
ARIN - American Registry for Internet Numbers
AFRINIC - African Network Information Center
APNIC - Asia Pacific Network Information Center
CNNIC
JPNIC
KRNIC
TWNIC
VNNIC
LACNIC - Latin America & Caribbean Network Information Center
RIPE - Reseaux IP Européens—Network Coordination Center
Websites
Infosyssec Database
Whois.net
Wayback Machine
Traceroute.org
DNS Stuff
Domain Tools
Geektools
Fixed Orbit
Kartoo - Metasearch engine that visually presents its results
Netcraft - Online search tool allowing queries for host information
Tools
On The Same Host (IP Lookup)
What Is My Current IP
Blacklist Check
Spamhaus Check
DIG LookUp
Open Mail Relay Test
Zone Files
MAC To Manufacturer
Internet Country Codes
Internet Health Report
Internet Traffic Report
Network Tools
DNSWatch
IP2Location
Sam Spade
Quick DNS Check
DNS Stuff
Domain Research Tool
Firefox AS Number Plugin
Subnet Chart
All IP Addresses By Country
Scripts To Block All IP Addresses By Country
HTML Color Chart
Security Related
Zeroday Tracker
Security Focus
Nessus Knowledgebase
FRSIRT
Snort Forums
SANS
Packet Storm