The IANA webpage will send you to the other top-level domain authorities.
E.g., it sends you here for .edu:
http://www.educause.edu/edudomain/
The ones for the country code domains (such as .uk or .fr) are a bit
hidden:
http://www.iana.org/cctld/cctld-whois.htm
(Two letter domains, such as .uk, .de and .jp (for example), are called
country code top level domains (ccTLDs) and correspond to a country,
territory, or other geographic location.)
The Internet Corporation for Assigned Names and Numbers (ICANN)
http://www.internic.net/
http://www.icann.org/registrars/accreditation.htm
Domain names ending with .biz, .com, .info, .name, .net or .org can be
registered through many different companies (known as "registrars")
that compete with one another.
Only registrars accredited by the Internet Corporation for Assigned Names and Numbers (ICANN) are authorized to register .biz, .com, .info, .name, .net and .org names.
ICANN is the new non-profit corporation that is assuming
responsibility from the U.S. Government for coordinating certain
Internet technical functions, including the management of Internet
domain name system. More information about ICANN can be found at
http://www.icann.org