1) Marriage to a United States Citizen (K Visa)
2) Spouses of Green Card holders (V Visa)
1) The 'New' K Visa
The reason for the new K visa is to help reunite families that have been or could be separated for a long period of time during the process of immigrating to the USA. This new visa allows K visa holders to wait in the US for this process to be completed.
The new additions to the K category are intended for use by both a spouse of a US citizen and by the spouse's children. For the spouse, the new visa will be called a K3 visa and for the spouse’s children will be called a K-4 visa.
The original K (fiance/e) visa category for the fiance/e of a US citizen will continue, though it will now be called the K-1 for visa purposes. The visa for a child who will be immigrating with a K-1 alien will still be a K-2 nonimmigrant visa.
Marriage to a United States citizen qualifies one for a green card. If the marriage occurs abroad, the green card petition must be filed through a U.S. Consulate with jurisdiction over the applicants place of residence. The procedures usually take between six to nine months to complete. Many newly weds, for a variety of reasons, don't relish the idea of six months of separation, or six months of waiting, before they can enter the U.S. as a married couple.
Although, the same process that takes 6-8 months abroad, takes 12-18 months in the US, the applicant may work and live in the U.S. from the date of filing. Thus the lengthy processing period is not as inconvenient as it would seem. Those who apply abroad must wait out side of the US during the entire processing period. As a result, many newly weds prefer to undertake the entire green card application process in the U.S., so that they can live together and work while they patiently wait for the bureaucracy to grind out the green card approval notice.
INS will not admit people who intend to live in the US permanently as a non-immigrant. The choice is to file the green card application abroad and come to the US as a permanent resident or come to the US as a non-immigrant tourist or worker, then marry and finally file for the green card in the U.S. In the later case, if INS knew all the facts, they would deny entry and possibly bar entry for five years under summary removal procedures. One may not enter the U.S. as a non-immigrant with the intent to live in the U.S. permanently.
Rather than force people to lie about the purpose of their entry to the U.S., in 1970 Congress created the K-1 or fiancee visa category. The K-1 visa avoids the risk of being denied entry to the U.S. or worse The K-1 visa permits a fiance to enter the U.S. as long as the marriage takes place with in 90 days of entry. The visa may not be extended so be sure to marry with in 90 days. The applicant may work in the U.S. during the 90 day period. Immediately after the marriage, the couple may file the green card petition, form I-130 and the adjustment of status petition I-485 with INS. The K-1 visa tends to reduce the INS processing period because the K-1 visa application process requires much of the same information the INS requires for the green card petition.
The U.S. citizen side of the equation files form I-129F on behalf of the intended by mail at one of the four INS regional processing centers. This form requires personal data or each applicant, proof the applicants have met with in the two years prior to application and a statement that the applicants intend to marry within 90 days of entry to the U.S. INS will make exceptions for arranged marriages if the applicants can show that arranged marriages are a long standing family custom.
If the petition is approved , INS will send the file to the Consulate nearest the residence of the alien fiance. The Consul will conduct security clearance procedures and then schedule an interview, much like a permanent residence interview. The applicant must supply pictures, a medical exam, and an affidavit of support. The green card interview and K-1 interview procedures are almost identical. If the Consul issues the visa, the supporting documents are put in a sealed envelop for presentation to INS at the port of entry. This same package can be used for the adjustment of status and green card application with INS after the marriage. The fiancee has 4 months from the date of visa petition approval to apply for the K-1 visa at a U.S. Consulate. Although the four month period may be extended, each extension requests casts doubt on the ultimate intention to marry in the U.S. The fiancee must either marry with in the 90 day period or leave the U.S. If the fiancee leaves prior to the expiration of the 90 day period and returns, he or she will only be admitted for the balance of the first 90 day period.

Fiancee dependents receive a K-2 visa, which doesn't permit employment but does permit attending school.

In summary, the K-1 visa is the legal way to enter the U.S. with the intention of marrying a U.S. citizen. Those who don't want to marry with in 90 days need to utilize a B-1/B-2 or non- immigrant work visa and need to hope the INS inspectors don't ask the right question.
For more Information and Application Forms and Fees - click here

2) The New V Visa
The introduction of the V1 and V2 nonimmigrant visas allows certain spouses of Green Card holders (lawful permanent residents) and the children of those spouses to travel to and from the US, and to stay in the US while they wait for the final completion of their immigration process.
It does not matter whether that process will be completed by adjusting status in the US or in securing an immigrant visa overseas. The spouse and unmarried children of Green Card holders who qualify for the V1 and V2 visas will be able to visit and stay with them in the US. For adults and children under the age of 11 the V visa will be valid for multiple requests for entry for ten years; for children 11 years old or older, the visa will be valid for multiple requests to enter and will remain valid until the holder’s 21st birth day. A major benefit of the V visa is that holders of V1 and V2 visas may apply for employment authorization documents to work in the US.
The V visa is not applicable for; brothers and sisters of lawful permanent residents, Parents of US citizens, Grandchildren of lawful permanent residents, Beneficiaries of employment-based immigrant visa petitions, Individuals whose priority date is current and whose I-130 petition is already at an overseas post and who either have already been interviewed by a consular officer or have an interview date already set with a consular officer overseas

For more Information and Application Forms and Fees - click here