This system let you perform any dns lookup you want: check online the results of dns queries and verify that your settings are OK
DNSQueries provides network tools and lets you make every needed network test, such as domain health tests, RBL checks, dns lookup, ptr queries, host geographical informations, dns query and many more
DNSQuery.org is a free, non-profit web site, targeting system or dns or domain administrators, to enable them make some queries via a candy web interface
DNSstuff offers DNS tools, Network tools, Email tools, DNS reporting and IP information gathering. Explore monitoring products and free DNS tools at DNSstuff.