A site that has all of the TLDs (traditional as well as kitchy new-school), what registrars you can get them through, and how much you can expect to pay at each of them so you can shop around.

The FAA's official search page for aircraft registration and ownership.

Transparent domain information, from AAAA records to WHOIS. Free DNS record, IP address hostname, and WHOIS lookups.

A Python module that implements a WHOIS client. Requires the futures module as a dependency. Returns what it finds as a Python data structure.

A website that acts as a directory to voter registration websites for every state in the US. You can either register to vote or check to see if your voter registration is valid and up to date.