t-mobile unlimited internet is $19.95 a month.
i have a nokia communicator phone the most recent is the e90. They have cards in them you can take out and stick in a computer and access the data just like a hard disk. Just carry an adaptor. This way you can quickly download any drive you need in the field.
I like the communicator series b/c they are more like a computer than an iphone. the 9300 was originally around $1000.00 u.s.d. but you can get them for 1/10 that on ebay now.
You can use it on a laptop as a bluetooth modem. I browse the web on it, irc on it, message on it, email on it, movies and music, etc. lol. But... for $19.95 t-mobile provides really fast internet and even with bluetooth to my laptop it's fast as being on a cable modem.
they just add it to your existing phone plan.

another cool thing about the communicators, is that can sync via bluetooth so your appointments, schedule, contacts, word docs, excel sheets, powerpoints, everything just perfectly synch's. So you can work on your business budget, or billing info on the go. you can even print to an infrared or bluetooth printer without wires. it also lets you control lcd projectors for powerpoint presentations remotely. you can even vnc into a pc from the beach and fix issues.

so anyway. It's really cool. the newer ones are even better. but this line of phones is so powerful it's like having your office in your pocket. the 9300 which cost originall $1175 i think is now about $100 on ebay, it can only use a 1 gig mmc card though, but the newer ones can use much larger. but for me a couple of 1 gig cards can carry plenty of info. i actually keep a few smaller mmc's for downloading drivers, and just use a mmc to pc adaptor to solve the "i need a driver in the field issue".
