Throwaway mail addresses
Were you ever in need of a mail-address to just receive THAT ONE mail and forget about that address afterwards? For example to create a one-time account somewhere to just download a simple demo of something (this nasty stuff seems to get used more and more in the net, but for what reason)?
Well, you can use such addresses without registration/creation, even without the need of login at:
Just take care to use a really one-time address and NEVER use it for important mails. Everyone can read it if he guesses the address!
If you want it extra-easy, Mailinator generates one-time address- suggestions for you on its frontpage, even with an instant-login link for that address. A'la firstname.lastname@example.org.