Basic network tools

Find your IP address and Locate any IP

Nslookup

Dig

Whois

Reverse DNS lookup

Ping

Traceroute

Server info

DNSBL-check (check spam source)

Useful links on the web

http://www.openpeering.nl/publicpeering.shtml

http://www.netconfigs.com/tools/analysis.htm

http://smokeping.eliott-ness.com/smokepinguser/smokeping.cgi?target=World