Excilan pay-by-phone portal and directory: I've been interested in the Excilan model for paying for a hot spot connection by cell phone for some time, ever since FatPort tipped me to it. In Excilan's system, partner wISPs have on their gateway page a place you can enter your phone number. If your cell carrier is one of those partnered with Excilan, your phone rings and an automated system tells you the price and confirms that you want to pay. When you confirm by pressing a button on your cell phone, the system authenticates all the way back to your particular session.
The reason this model is interesting is that it doesn't require a user login or other authentication. It lets cell carriers partnered with wISPs charge whatever they want above the wholesale rate -- which could be a tiny markup if they're just trying to show off new uses. And the user gets the charge on their cell phone bill, making it easier to have it reimbursed if they work for a business.