Hello
I would like to register some .US domains but I am not US citizen so I
need US firm.
Can I register US firm from Europe or even online.
What kind of firms I can register and which one would be most suitable.
Do I have any obligations if I don't use this firm.
How much does it cost and how much time does it take.
Regards
Nik

Here are the requirements for registering a .US domain.

"Registrants in the usTLD must be either:

1. A natural person (i) who is a United States citizen, (ii) who is a
permanent resident of the United States of Ame rica or any of its
possessions or territories, or (iii) whose primary place of domicile
is in the United States of America or any of its possessions,

2. A United States entity or organization that is (i) incorporated
within one of the fifty (50) U.S. states, the District of Columbia, or
any of the United States possessions or territories, or (ii) organized
or otherwise constituted under the laws of a state of the United
States of America, the District of Columbia or any of its possessions
or territories (including a federal, state, or
local government of the United States or a political subdivision
thereof, and non-commercial organizations based in the United States),
or

3. A foreign entity or organization that has a bona fide presence in
the United States of America or any of its possessions or
territories."

http://www.internic.ca/faq/help.asp?q=what+are+the+ustld+nexus+requirements%3F

to follow up on the other comment, to get a list of firms that sell
.US domain names visit:

http://www.internic.com/alpha.html