No Contract Cell Phone Providers in US:
Verizon Wireless. User ranked #1 cell phone provider. Most reliable cellular network in US and superb customer service makes Verizon Wireless number one choice for many people. They offer few no contract plans and fantastic range of new cool phones. Prepaid (no contract no credit card) plans start for as low as $44.99 and include 450 minutes. If you want data access, unlimited allowance plan will cost you $30. My personal favorite is brand new 4G cell phone – HTC Thunderbolt. Tho this is not cheapest prepaid phone provider, but superb network speed and reliability makes this my personal favorite.
AT&T Wireless. Probably biggest selection of available phones, country-wide network presence, tho network reliability can be spotty in some regions. AT&T customer service does not have the best reputation tho real issues are noted by very few users. AT&T have excellent prepaid and no contract cell phones and smartphones. Basic prepaid phone starts as low as $9.99 and AT&T offers great variety of plans including $2 unlimited daily talk and text and even pay as you go with easy top up options. They also have reasonably priced no contract smartphone selection – definitely worth checking out! I think those 2$/day plans are great for chatterbox kids! 
P.S. AT&T is named worst cellular communication provider in 2011 by consumers report, so please take that in mind when considering this one!
T-Mobile. Offers good choice of no contract phones and have very reasonable no contract plans – for $30/month you will get 1500min talk time and text (any combination of talk minutes or messages) plus 30Mb of data. For $70 you will get unlimited talk and text with 2Gb data – cool plan for smartphones. T-mobile also have variety of pay as you go refills starting with just $10 for 30min of talk. Please check 3G availability in your location as T-Mobile is still slightly behind on the 3G coverage.
Boost Mobile has probably best Boost unlimited plan. Just for $50 (that gets cheaper as you stay with Boost – for example, after 12 payments it will be just $40) you will get unlimited nationwide talk, text, web, 411, IM and email with no contracts. Voice mail, long distance and call waiting included. Boost is owned by Sprint Nextel and uses its network as far as I am aware. The only thing that I do not like about Boost is phone prices and somewhat limited selection. Aside from that, definitely worth checking out, especially, if they run some promo or have discounts.
Cricket have very competitive pricing but network coverage have its limit and that can cause pretty steep roaming charges so, be careful with roaming. Basic Cricket no contract Unlimited plan starts at $35 and includes talk, long distance, text, voice mail and caller ID. They also offer free overnight shipping to all 50 states with new phone purchase. Cricket finally offers smartphones – Android and Blackberry and according plans – smartphone plan will cost you $55/month and includes some really cool features. Check their coverage map to avoid roaming charges.
Virgin mobile have great data-oriented and text plans but voice calls are slightly more expensive than competitors but its really great for smartphone users – for just $25/month you will get unlimited data, text, email and web but only 300 minutes talk. If you are smartphone user and use more messaging and social network to communicate, this might be best choice for you. Virgin also offers really good deals on smartphones and of course, its all no contract.
Metro PCS have probably some of the cheapest unlimited calling plans, but it is available only in certain regions and, of course, roaming charges will add up. But, if metro PCS is available in your location, this can be great choice. Metro PCS also have great choices of 4G smartphones for very reasonable prices and unlimited 4G plan is only $60/month and have some cool features like 4G video on demand for some Blackberry phones. They also have very decent prices for mid-range smartphones and some really cool 4G phones like Samsung Galaxy Indulge for just under $300. Of course, they offer this all without any contracts. Verdict – metro PCS can be really cool choice if their service is available in your location!
TRACFONE offers very basic but really cheap phones but their cost per minute is relatively high compared to competitors. For example – touchscreen LG phone will cost you just $49.99, basic Samsung phone will be just $10. Basic fliphone and 60 minutes talk time will be just $19.99. While TRACFONE wont be best choice for lengthy calls, it can be extremely useful as an emergency phone in your car or, for instance, if you need a cheap phone with number just for one time deal selling real estate and font want to put your personal phone number on ads.
This sums up major no contract cell phone provider list for the USA. It is compiled 4/2012 using data from the phone company websites. Please note that as time passes, everything (in theory) should get cheaper and better, so accuracy of this data will diminish with time, but it will still be a good checkpoint. And please note that switching from 2 year contract to no contract cell phones with any of these providers can save you great deal of money in a longer run.