[nnnnni]

Hello, my name is Guy Incognito. My email address is [e-mail].

Unless it requires you to click a confirmation link or something similar to that, just use a fake address at one of the example.TLD domains.

If they DO require confirmation, use mailinator or a similar service.

[sbierwagen]

Catch 22 there: you have to be able to access mailinator.com in order to generate a throwaway email.

[refurb]

Not with mailinator. You just choose a username and it gets sent there. No need to go to mailinator.com first.

[userbinator]

Requiring email confirmation assumes the fact that the user can already connect to the Internet to access his/her email to read the message, throwaway account or not, so that wouldn't work too well...

[nnnnni]

Connect with your phone long enough to confirm?

[smsm42]

Possible, but never seen free wifi actually do that.