Professional Visas
If you are a professional or a fashion model, an employer can petition for you to have an H-1B visa. This visa can last up to 6 years. In most cases the position requires a college degree, but there are exceptions and experience may be considered instead. There are many other conditions, such as the commitment from the employer to pay the prevailing wage and the occupation of the alien which must be a specialty occupation. Finally, this type of visa is employer dependent and non-transferable.
Certified nurses can also have an H1C visa, which follows specific requirements.
Many foreign companies that establish or have existing subsidiaries in the U.S. can transfer key employees to the American office on an L-1A or L-1B visa. There is a requirement that the employee must be employed in the foreign company for at least one year in the previous three years prior to the transfer. These visas are currently highly scrutinized by the Bureau of Citizenship and Immigration Services (BCIS) because fraud is becoming rampant.
Another popular visa is the E visa for investors. Foreigners who substantially invest in our country or who conduct substantial trade with us can reside here on an E visa provided the U.S. has a treaty with their country permitting such investment or trade. The E visa is valid for as long as the investment or trade is valid. See more here.
Student Visas
Students may reside here on F or M visas which require that the applicant goes to school full-time at a school recognized by the BCIS. Most public schools and colleges qualify for this visa (although some do not accept any more foreign students). However, if the student is in public elementary or high school, there will be a tuition charged for attendance. Most students are not allowed to work. But it is possible to get a work permit after one year of studies under certain circumstances. Even then, the student may only work for 20 hours/week.
After the terrorist attacks on the U.S. soil on September 11, 2001, a new regulation has been enacted and this means that every case is highly scrutinized which delays the process. As a result, do not make plans to come to the U.S. unless you have your visa in hand. This advice is equally valid for all visas.
International exchange visas also exist, such as J visas and Q visas.
Family Visas
The K visa is issued to a fiancée/fiancé of a U.S. citizen who is planning to marry an alien. This visa permits the alien to enter the U.S. to get married, a ceremony which must take place within 90 days of entry. Once the immigrant gets married, he or she must go to the local BCIS office for an interview to get the green card.
The V visa has been created in the same time to avoid the cruel separation of spouses and children of green card holders.
TN visas have been established for Canadians and Mexicans, beneficiaries of the North American Free Trade Agreement (NAFTA) which allows them to stay and work on the U.S. territory under specific requirements.
Special Skills
There are other temporary visas such as the O visas and P visas designed specifically for athletes and entertainers of extraordinary skill and ability.
All of the "letter" visas have their own specific procedures and requirements. The list provided here is not exhaustive and we may find a visa that is specifically fit to your situation.