Web Tools

AnalogX: DNSDig
DNSDig is a web version of dig. Allows queries for a domain's DNS from any machine on the Internet.
http://www.analogx.com/contents/dnsdig.htm

CheckDNS
Online utility for DNS administrators. Test your DNS servers, domain registration, mail and web servers.
http://www.checkdns.net

Codeflux Internet Tools Gateway
A gateway for: finger, nslookup, WHOIS, SSL, traceroute, ping, and dig.
http://codeflux.com/exec/tools/

DNS Bajaj
Check the delegation of your domain. Has interesting graphical results.
http://www.zonecut.net/dns/

DNS Report
Provides a free DNS report on your domain name, verifying that your DNS hosting is working properly. Includes over 40 different tests, looking for both minor and major problems.
http://member.dnsstuff.com/pages/dnsreport.php

DNS Search Gateway
Handy web-based DNS lookup service, with links.
http://cgibin.erols.com/ziring/cgi-bin/nsgate/gate.pl

DNS Stuff
Many free web-based DNS and domain name tools all in one location. Includes standard DNS lookups, WHOIS/IPWHOIS, and even obscure DNS hosting tests, IPv6, IP-to-country and spam database lookups. Fast and thorough.
http://www.dnsstuff.com/

eLiteral - Web Utility
Provides ping, traceroute, whois, finger, nslookup, and dig.
http://www.eliteral.com/moveditems/webutil/

Global Whois
A WHOIS domain name search. Check domain name registrations, look up domain names, IP addresses, nameservers, registrars, etc.
http://www.ratite.com/whois/

iWEBTOOL
iWEBTOOL has frequently used web tools. Tools ranging from a rank checker to HTML encrypter.
http://www.iwebtool.com

Kloth.net NSlookup
Web-based nslookup tool that lets you look up IP address information. Query their and other DNS domain name servers to look up and find IP address information of computers on the internet.
http://www.kloth.net/services/nslookup.php

Lookup Server
Provides basic forward and reverse DNS lookups, as well as MX record and server software lookups.
http://www.lookupserver.com

Name Server Zone Transfer Tool
Free tool to check the security of any name server. Requests a name server zone transfer for any domain.
http://www.digitalpoint.com/tools/zone-transfer/

Sitegizmos Webmaster Tools
Sitegizmos provides some DNS tools, as well as some other tools useful to webmasters.
http://www.sitegizmos.com

squish.net DNS Checker
Complete DNS traversal check. Shows every DNS server that is (or maybe) used for a DNS lookup.
http://www.squish.net/dnscheck/

Web-Based NSlookup page
You can query any domain here to find the DNS information similar to a nslookup. Links to whois information.
http://www.enc.com.au/itools/nslookup.php