Domain Tools – Excellent site for researching domain and registrar info
IP Tools – IP, DNS, internet, WHOIS, trace route, ping, domain name tools
DNS Information – Query Your Domain and IP Information
intoDNS – Checks DNS and mail servers health
Squish – Complete DNS traversal checking
w3dt.net – World Wide Web Domain Tools
DNS Queries – The complete toolset for every network admin
Netsys Tools – Clean site design with some good DNS/IP tools
Network-Tools – Trace route, Ping, DNS lookup, WHOIS and DNS Records Lookup
Central Op’s – Free online network utilities
DNSBL.info – Spam database lookup
Tools.webmax.ca – Another spam database lookup site
Other Useful Sites
Is it down for everyone or just me? – Handy site to see if there maybe routing issues from your ISP