Let the hive mind of Engadget get that for you.
"As someone who doesn't reside in the USA, I was wondering what would be the best way to get internet for my computer in the US for a couple of weeks? If it were Europe I know I'd look for some prepaid data. Is there anything similar offered by American carriers? A MiFi or a data SIM that I can tether from would work, but I'm trying to maintain a tight budget. Help!"
Don't we already have a very reasonably priced, immediately available, Mobile Internet Device (MID) called the iPod Touch?
I played with a iPod Touch two days ago at the local Apple Store - and for $299 it's certainly the equivalent of an Nokia N800 and many of the other webpads that I've played with for half the price.
Apple may not have intended this to be a MID or 'webpad' but I'm seriously considering deploying some of my web-based apps using iPod Touch devices since they're cheaper and easier than buying a PC with a touchscreen.
Unless the six devices above do something more interesting than connect to a wifi network and allow one to surf the web, IM, play music or video streams over the network. The only I can imagine they are likely to do is provide an API allow a user to load an arbitrary 3rd-party application. Of course, with the advent of the installer.app the iPhone now has this feature too (until Apple disables it with a firmware upgrade).