US Embassy US Consulates around the world 
See the piece on US Immigration fraud. Immigration fraud will always be around as there is money involved in the process and also fraud become a national security issue in the world we live in today. These are what you should be aware of. Ensure that you do not fall and be scammed by immigration consultants.
USCIS
USCIS stands for United States Citizenship and Immigration Services, which is an agency within the Department of Homeland Security (DHS) responsible for overseeing lawful immigration to the United States. You will note that the USCIS handles all the applications and petitions for immigration benefits. These including citizenship, permanent residency (green card), temporary visas for work as well as study.