This topic has been discussed here frequently. However, the goal posts are always moving as technology "advances".
I have a particular interest in it as my wife and I embark on an eight month journey volunteering at national and state parks next Spring. I came across this blog post that I found interesting that I think others might be interested in as well:
Getting Online On The Road -> The Mobile Internet Handbook | Wheeling It
The authors of this blog are young full-timers from the tech world and they know their stuff. Hope it helps.