Boingo Wireless has a new app for the iPhone, iPod touch, and, soon, the iPad that lets you buy an hour of service at a time: The Boingo Wi-Fi Credits app will let you connect from any iPhone OS device for $1.99 for 60 minutes at a single location in Boingo's aggregated worldwide network. You can also purchase 11 credits for $19.99.
Boingo has a $7.95 per month mobile plan that all iPhone OS devices qualify for; the company reiterated today that the iPad would be supported out of the gate. That's why two bucks for one hour seems a bit steep, since Boingo doesn't require a contract commitment to use its mobile service.
The only other worldwide pay-as-you-go system is Skype Access, formally launched a few days, which charges US$0.22 per minute for on-demand access. (See my article from 18 March 2010.)
The folks at Trustive also have pay as you go, prepaid plans for occasional travelers, in addition to subscription plans. They also have a large network.