Mailinator
For when you have to add an email to get that download. You don't have to visit the site beforehand. Just fill in the email with anything@mailinator.com and then visit the site and check anything's box. Simple, no password, no fuss.
You can also use:
* mailinator2.com
* sogetthis.com
* mailin8r.com
* mailinator.net
* klassmaster.com