Mailinator

Mailinator is incredibly useful. Oftentimes a site ask for your mail adress, and you really don't want to give it. Then you put in

'whatever@mailinator.com'

and open www.mailinator.com in a new tab/window. Input 'whatever' and access the open mailaccount which is created as mail arrives, and deleted at a couple of hours intervals. No password. Open your acknowledgement mail. Presto.