U.S. Citizenship and Immigration Services website: offers information regarding Immigration Laws and procedures. 

Online Forms:
USCIS Downloadable forms are available on this website. Please note that you will not be able to file some of these forms via the Internet -- you will have to print out the form and mail it to the appropriate USCIS office. 

Department of State Visa Services: Department of State's information web pages about visa, e.g. Waiver of the J Visa Two-Year Foreign Residence Requirement,  Visitor Visa Application,  Visitor and Student Visas, Immigrant Visas, Employment Visas, Revalidating Visas in the U.S. and more.

Visa Appointment Reservation System: A system for booking non-immigrant visa interviews. Interviews may be booked at the U.S. Embassy in Ottawa, Canada and selected Consulates and Consulates General in Canada and Mexico.