Traveling Abroad from the United States

U.S. Citizens

Passports
U.S. citizens typically need a passport to enter a foreign country. Passports should be valid for six months beyond the scheduled visit.

Visas
U.S. citizens may be required to obtain a tourist visa to enter certain countries. Entry and exit requirements for U.S. citizens traveling abroad is available from the U.S. State Department. Entry and exit requirements are also available by contacting embassies and consulates in the United States directly.
Country Specific Information from the Department of State

Traveling to Canada
Everyone who enters Canada is required to provide proof of identification and citizenship. A passport satisfies these requirements, but U.S. citizens may also provide other specific forms of identification to meet these requirements. In most cases, if making a short trip to Canada, U.S. citizens do not need a visa.  
Requirements for Traveling to Canada
Admissibility and Required Identification

U.S. Visitors and Residents

Foreign nationals must review their immigration documents before leaving the United States to make sure that they will be allowed to reenter.

Advance Parole
It is very important that foreign nationals who have applied for adjustment of their immigration status to U.S. permanent resident to obtain "advance parole" from U.S. Citizenship and Immigration Services if they plan to travel abroad. Without advance parole, they will abandon their adjustment application and will not be readmitted to the United States.
Advanced Parole Tips from DHS
Advanced Parole from Customs and Border Protection

Visa Requirements
Travelers should determine well in advance whether they require a visa to enter their destination country. If a visa is required, contact the respective embassy for information on visa application.

Academic Institutions
If your institution has an international office, it may offer additional guidance. For example, a student on an F-1 visa should consult the international office at his/her university.

Travel to Canada
Everyone who travels to Canada must provide proof of citizenship and identification. Travelers should also determine whether they will require a visa.
Canadian Visa Requirements
Canadian Visitor Visa Information