DNSstuff is a web site with DNS tools, reports and Hosting tests, advanced network and domain name tools. Top 3 tools are:
1. DNSreport: Provides comprehensive information about the specified domain that may verify DNS ‘health’ or identify problems or issues;
2. WHOIS Lookup: Finds contact information for the owner of specified domain/hostname, and
3. Reverse DNS: Determines the hostname associated with a specified IP address
Very useful for geeks, but also for anybody who is interested to find out how their Internet provider is working.