I believe if you want a card, all companies are running at $59.95/$59.99 a month. Usually requiring a 1 or 2 year contract.
Tethering to a phone with either a cable or bluetooth will be cheaper but will give you the disadvantage of not being able to use your phone while on the internet. Usually the unlimited plan when tethering to a phone will be about $20 cheaper per month.
I've been using wireless data since the beginning of the technology back when AT&T was the only provider on analog data. Its my opinion that Sprint is the best choice. They have speedy EVDO Revision A data, which may be important for anyone who uploads video in the field. Upload speeds on EVDO Rev A can be on the order of 2x the upload speed you get with a cable modem. Downloads are comparable to DSL.
Sprint also has great partner agreements. This is where your choice in a provider is crucial. Research their partner agreements. For storm chasers who need to traverse the whole mid section of the nation, you want someone who can provide seamless data even off their own network. Everyone provides unlimited data roaming without additional fee, so don't be afraid to go with someone who has a lot of roaming partners.
Sprint's biggest allies in this are AllTel and Verizon. If you like AllTel or Verizon, they are also great choices as I believe all 3 companies have backwards compatible roaming agreements. So if you get a plan with any of these providers, you'll get to roam on all 3 networks. So look at the coverage maps. Generally they will include any roaming areas as a part of their native network. Sprint does this. So if you look at the Sprint coverage map, it will show a lot of coverage. Much of it is roaming on other networks, such as Verizon and AllTel, but that's ok because there are no additional fees, and you as a user won't even notice when you're switching to their towers. Works seamless and unnoticed.
Thats a big reason not to go with someone like Cingular/AT&T or T-Mobile. Although GSM has been the leading technology across the world, CDMA is the leading technology in the US, and therefore there are more companies using CDMA for a company to partner with. AT&T is basically by themselves with GSM, so they have to put up their own towers. Companies like Sprint just need to sign a contract and they light up several thousand more towers that you can use. So what it means in the end is much better coverage. If not now in your area, it probably will be that way in the future as this is the leading technology here.
Also, regarding speed of data, HPSA (abbreviation may be incorrect) is the technology for GSM and it is not as fast as the competing EVDO on the CDMA networks. So not only do you get better coverage, but faster data.
If you really want to get into the subject, visit evdoforums.com. You can make your mind explode with all the info you could want on the subject.
As a footnote, I'd add that my recommendations are for storm chasers traveling a lot of ground. Do not take this advice if you're just looking for coverage for your cell phone. I use Sprint for both my data and voice, but the advice for voice is the old standard.... check out the high resolution maps for where you LIVE and if they have good coverage and price in your neighborhood, then its a good choice.
A good company with lots of towers and speed nationwide is going to do nothing for your cell phone if they don't have a tower where your house or work is.
