I would like a list of colorful Web sites run by tribes of first the
north Texas region and moving north from there to say Montana until
about 10 sites are counted. These sites should have as mission
representing their culture to the wider world.

Dear stackrat5,

The search was not easy, since most official websites owned by Indian
tribes deal rather with current issues than with the cultural
heritage, as I found out. However, I did my best to locate at least 10
sites from tribes between Texas and Montana that should prove useful
for you:

-- Texas --

- The Alabama Coushatta Tribe of Texas -
http://www.alabama-coushatta.com/
This tribe is, unfortunately neither located in northern Texas but
rather in the eastern part, nor is the website particularly colorful
or focussed on cultural topics. But I decided to include it here for
reference purposes.

-- New Mexico --

- The 19 Pueblo Tribes -
http://www.indianpueblo.org/
The 19 tribes of the Pueblo Nation own and operate the Indian Pueblo
Cultural Center Website, dedicated exclusively to presenting their
culture to the world.

-- Oklahoma --

- The Chickasaw Nation of Oklahoma -
http://www.chickasaw.net/
The Oklahoma Chickasaw website has an extensive category "Heritage &
Culture", with sub-categories on various cultural and historical
topics.

- The Cherokee Nation -
http://www.cherokee.org/
Though the general appearance of the official Cherokee website is
modern and not adorned by traditional elements, there is very
extensive information on the tribe's culture and history in the
respective categories.

- The Delaware Tribe of Indians, Oklahoma -
http://www.delawaretribeofindians.nsn.us/
A plain website with few graphics, but with information on the tribe's
cultural and historical background.

-- Kansas --

- The Prairie Band Potawatomi Tribe -
http://www.pbpindiantribe.com/
Has interesting information on the tribe's culture and history.

-- Colorado --

- The Ute Mountain Ute Tribe -
http://www.utemountainute.com/
The section dealing history and cultural heritage is still rather
meager. However, this is the only official tribal website from
Colorado I could find, so I included it here.

-- Nebraska --
 
- The Winnebago Tribe of Nebraska -
http://www.winnebagotribe.com/
The explicit cultural information is (yet) a bit exiguous, but the
website is nevertheless quite attractive and informative.

-- North Dakota --

- The Standing Rock Sioux Tribe -
http://www.standingrock.org/
The very first item in the list of categories is the not very
extesive, but interesting overview of the tribal culture and history.

-- Montana --

- The Blackfeet Nation -
http://www.blackfeetnation.com/
The official Blackfeet website is in the process of re-designing at
the moment, but according to the announcement, the future emphasis
will be the rich culture of the tribe.

In case you need more official tribal websites, I recommend using
these directories, like I did for answering this question:

Tribal Contacts, Geographical Index
http://www.hanksville.org/sand/contacts/tribal/US.html

Tribal Fires: Native American Official Web Sites Search Engine 
http://tribalfires.com/search/

Google Web Directory: Native Americans - Tribes, Nations and Bands
http://directory.google.com/Top/Society/Ethnicity/Indigenous_People/Native_Americans/Tribes,_Nations_and_Bands/

Hope this is what you were looking for!
Best regards,
Scriptor

Great search work! You just got me going! I'll be back for more.