I know there are some services such as those offered by T-Mobile that offer unlimited GPRS for a $30 or so monthly fee... what I'm wondering is, what's the BEST service to use for unlimited laptop connectivity anywhere in the US?

I'm planning a 2-3 month trip this summer, and I'd like to stay connected (email, maps, etc) to the net wherever I am.

Anything a non-US resident can buy to have unlimited Internet anywhere for a flat monthly fee?

-Lee