How delighted I was when I was in the US last year that AT&T had a prepaid Internet access offer that worked pretty well for me. Unfortunately, it didn't last long and AT&T abandoned the tariff after a couple of months. Quite a disappointment. But now it seems AT&T has come back to prepaid land and offers a 100 MB package for $19. Not as good as their original offer and certainly nowhere comparable to much better offers in other countries but for many purposes quite useful. For the details check out the Prepaid Wireless Internet Access Wiki here.