The Internet Corporation For Assigned Names and Numbers (ICANN) provides registrars, registrants and the general public with information and general support with regard to ICANN-accredited registrars, and the ICANN RAA. ICANN also assists prospective registrars with preparing and reviewing their accreditation applications, as well as maintaining registrar accreditations and ensuring registrar compliance with RAA obligations. The latest version of RAA (Registrar Accreditation Agreement) is the 2009 version.
According to ICANN there are currently 1022 accredited registrars. These companies have been accredited by ICANN to act as registrars in one or more TLDs. The ICANN accreditation only applies for gTLDs.
In 2002 I was able to contact most of the accredited registrars and use them in .info LR2. But those days are over. From 2003 to 2007 registrars jumped from about 150 to about 900. Many of these registrars were ghost registrars used for drop catching by big companies such as BuyDomains or by drop catching services such as Snapnames or Namewinner. Accredited registrars are still growing and a lot of them are still used only for drop catching.
ICANN currently accredits domain-name registrars for the following Top Level Domains:
.aero, (reserved for the global aviation community) sponsored by Societe Internationale de Telecommunications Aeronautiques (SITA INC USA)
.asia, (reserved for the Pan-Asia and Asia Pacific region) sponsored by DotAsia Organisation
.biz, (restricted to businesses), operated by NeuStar, Inc.
.cat, (reserved for the Catalan linguistic and cultural community), sponsored by Fundació puntCat.
.com, operated by VeriSign, Inc.
.coop, (reserved for cooperatives) sponsored by Dot Cooperation LLC
.info, operated by Afilias Limited
.jobs, (reserved for the human resource management community) sponsored by Employ Media LLC
.mobi, (reserved for consumers and providers of mobile products and services) sponsored by mTLD Top Level Domain, Ltd.
.museum, (restricted to museums and related persons), sponsored by the Museum Domain Management Association International (MDI)
.name, (restricted to individuals), operated by Verisign Information Services, Inc.
.net, operated by VeriSign, Inc.
.org, operated by Public Interest Registry
.pro, (restricted to licensed professionals) operated by Registry Services Corporation (dba RegistryPro)
.tel, (reserved for individuals and businesses to store and manage their contact information in the DNS) sponsored by Telnic Limited
.travel, (reserved for entities whose primary area of activity is in the travel industry) sponsored by Tralliance Registry Management Company, LLC
.xxx, (reserved for online adult entertainment) sponsored by ICM Registry, LLC