Verizon, the largest cell phone operator in the United States, uses the CDMA technology in its cell phones. It offers digital service in high density population areas and analog service in rural areas of the country.

Sprint also offers cell phone services on a nationwide CDMA network. It offers digital service in high density population areas as well as analog service in rural areas across the country.

Nextel offers phones specialized in push-to-talk technology and works on a nationwide network. Its iDEN cell phones, manufactured by Motorola, let users operate their phones as long distance two-paging devices. Thus, not only can they make calls, but they can also talk to each other instantly by pushing a button, just like with two-way radios. The Nextel cell phones do not include analog roaming facilities.

Cingular also provides cell phones on a nationwide network. It uses GSM technology.
Cingular cell phones being GSM, they are not designed for analog roaming in rural areas so service may sometimes be limited to urban areas.

T-Mobile cell phones work on the world standard GSM/GPRS technology. Coverage is mainly limited to urban areas. T-Mobile used to be called Voicestream but was bought by German company T-Mobile.

You can get handsets of your choice from any brand to get services from these operators. Handsets makers Palm, Motorola, Samsung, Sprint and LG Electronics are selling cell phones with all these latest features in the US market. Motorola, maker of the Razr and other popular handsets, is one the top brands.