This tool shows which countries and top domains are related.

Select a domain (ex. dk) or a country (ex. Denmark) and see the corresponding value pop up in the other drop-down box

After selecting the relevant domain in one of the two drop-down boxes, you can click the button to view the homepage of the domain administrator, either to read in depth about the domain or simply to register your own subdomain.

If you want info on a specific domain (ex. yahoo.com), you should use the domain lookup tool.