OnLine Tools

dnsreport.com

dnsstuff.com

grc.com
Open Port Tests

ordb.org/submit
Open Relay Test

directupdate
Great little tool for Updating Dynamic IP Info

www.2wire.com www.dslreports.com
speed tests

http://www.infosyssec.com/infosyssec/ipsectools.htm
whois, nslookup, nmap from their site

www.samspade.org
spam tracing tools