Netbook and ultralight don't really belong in the same subject line.
But, I'll play.
If I were world touring or cross country touring I'd likely use my iPad, add a camera kit for snagging photos off an SD card, and my G12.
Or get one of the new iPods, they've update the camera in those I think. Wifi, apps, ability to email.
You can get pay as you go iPhones.
http://www.wired.com/gadgetlab/2012/06/virgin-mobile-iphone/Or maybe the Samsung camera, of you can get it without a mobile contract:
http://mobile.theverge.com/2012/8/29/3276302/samsung-galaxy-camera-announcementOr the Nikon?
http://mobile.theverge.com/2012/9/18/3346812/nikon-coolpix-s800c-hands-on-android-cameraOr the Samsung galaxy note?
Really depends on what you want to do.