The DomainTools Whois plugin will automatically link domain names in a WordPress page or blog post to the DomainTools Whois service. It also generates a pop-up containing a summary of Whois information that your visitors can see without leaving your site.

DomainTools Whois Plugin

DomainTools whois plugin shows whois data for domains found in blog articles and links them to whois.domaintools.com.

ppatux

Simple IPv6 detector widget for WordPress to show if user is connecting with IPv6 or IPv4.
Additionaly, it makes a link to a whois service with the ip address.
It was born because of my own blog. I needed to include a little box that shows users ip and different messages depending on the ip version.
The idea behind this is to promote and leave a way to discover and make sense about the ipv4 address space limits.

IPv6 Detector

Simple IPv6 detector widget for WordPress to show if user is connecting with IPv6 or IPv4.

DomainTools Whois Plugin vs IPv6 Detector