BIND has a number of tools for testing and diagnosing problems such as named-checkzone, named-checkconf, rndc, nslookup and dig. This article explains how you can use nslookup and dig to diagnoze a domain or two. Read Article

whatsmydns.net is an online service that allows you to instantly perform a DNS lookup to check a hostnames current IP Address and other DNS information against a selection of random name servers around the world. This is especially useful to check the current state of DNS propagation after making changes to your domains zones.

Go to the site: http://www.whatsmydns.net