Tier 1 ISP in the world and Each country ISP in the world

North America

• U.S.

    - AT&T

    - CenturyLink (formerly Qwest and Savvis)

    - Cogent (formerly PSINet)

    - GTT (formerly Tinet)

    - Level 3 Communications (formerly Level 3 and Global Crossing)

    - Sprint

    - Verizon Business (formerly UUNET)

    - XO Communications

    - Cogent communications

• Mexico

    - Bestel

South America

• Brazil

    - ALOG

    - Internexa Brazil

• Argentina

    - LANautilus

Europe

• New Zealand

    - Telecom New Zealand

    - Telstra Clear

• U.K.

    - British Telecom

• Sweden

    - TeliaSonera

• Germany

    - Deutsche Telekom

• Spain

    - Telefonica

• Finland

    - TeliaSonera

• France

    - France Telecom

• Portugal

    - Portugal Telecom

• Russia

    - Maccomnet

APAC

• Singapore

    - SingTel

    - StarHub

• Japan

    - NTT

    - Softbank

   - KDDI

• HongKong

    - PCCW

    - PACNET

    - HK Telecom

• China

    - China Telecom

    - China Unicom

    - China Mobile

• South Korea

    - Korea Telecom

• Vietnam

    - VDC

    - FPT Telecom

    - Viettel Telecom

• Australia

    - Telstra

    - Optus (SingTel)

    - OzEmail (Verizon)

    - Connect.com (Telecom New Zealand)

• Turkey

    - Turkish Telecom

    - Super Online

    - Smile ADSL

• Indian

    - Aritel

    - Reliance

    - Tata

• Indonesia

    - NAPINFO

    - CBN

• Qatar

    - Qtel

• Irqa

    - IQnet

    - ETH Zurich

• ISRAEL

    - BEZEQ

• KUWAIT

    - Qtn

• Ghana

    - Ghana Telecom

• South Africa

    - Telekom South Africa

    - MTN

    - Vodacom

    - Neotel

I am sure that I am missing some.