Abuse.net
all-nettools.com
ARIN whois
betterwhois.com
www.blacklistalert.org
completewhois.com
DNSstuff lookup tools
DShield status page and port reports
Internet health report
Internettrafficreport
Codeflux internet tools
Speedguide.net - Online tools
Dsl Reports tools
DrTCP - from Dsl reports
EhcoEhco Web Tools - HTML checker
Gibson Research - Spinrite, patchwrk, leaktest and more
Iana port numbers
Interesting web sites for Internet Monitoring 
ITtoolbox Networking 
The JavaScript source 
Keynote.com scoreboard
 Looking glass - Conxion
neohapsis.com port list
Internic whois
Arin whois
Geektools traceroute listings 
Geektools whois
Openrbl.org
Openrbl lookup

testmy.net - download/upload test
Webcrawler
Wisenut search - does better then google for obscure web pages

Boneyard:
Looking Glass - digex.net 
Osirusoft rbcheck spammer lookup
Alhosts visual traceroute utility