Online Tools

Find your public IP:
http://whatismyip.com
http://myipaddress.com

IP location look up:
http://www.geobytes.com/IpLocator.htm?GetLocation
http://www.websitegoodies.com/tools/geoip.php

performance check:
http://www.websiteoptimization.com/services/analyze/
http://alertra.com/spotcheck.php
http://www.siteuptime.com/users/quickcheck.php

Broken Link check:
http://www.websitegoodies.com/tools/linkcheck.php

Speed check:
http://www.speedtest.net/
http://www.websitegoodies.com/tools/speed-test.php

Some good tools:
http://www.websitegoodies.com/tools.php

Check for black listing
http://www.mxtoolbox.com/blacklists.aspx
http://www.au.sorbs.net/
http://dsbl.org/main
http://spamblock.outblaze.com/
http://www.spamcop.net/
http://www.spamhaus.org/index.lasso
http://njabl.org/lookup.html

PING test
http://network-tools.com/
http://www.websitepulse.com/help/testtools.ping-test.html
http://www.selfseo.com/ping_test.php
http://www.buildtelligence.com/online-ping-test.htm

Zone Lookup
http://www.zoneedit.com/lookup.html