The Common Application - Over 500 colleges and universities worldwide (majority in the U.S.) accept The Common Application. The application is completed online and submitted electronically to the colleges and universities to which you apply.
UCAS - Universities & Colleges Admissions Service is the on-line service for processing applications for most colleges and universities in the United Kingdom. In addition this site can help with the selection process, searching for college majors and answering many of the questions you might have about studying in the UK.
Ontario Universities' Application Centre - The OUAC, located in Guelph, Ontario, Canada, is a central bureau whose key function is the processing of applications for admission to the province’s universities.
University of California - One application can be completed on-line and submitted to as many of the 10 UC schools to which you will apply.

Below are the links to lists of all the colleges/universities in different regions of the world.  Clicking on the link will take you to a site that lists all of the institutions in that country/region and provide you with a link to that institutions website:
List of US colleges/universities (4 year degree)
List of Accreditations for US Universities and Colleges (2 year degree)
List of Canadian Colleges/Universities
List of UK Colleges
List of UK Universities
List of Australian Universities
List of Australian Colleges
List of European Universities (by country):  On this site you have to scroll down and click on the country you are considering.  Once you click on a specific university, the website is listed.
List of Universities in the Middle East
List of Colleges/Universities Worldwide: This site includes over 6, 300+ universities around the globe and provides links to their websites.