I've released AnonyMail 1.1.3 for Ubuntu. AnonyMail is a small application that's available for Ubuntu (or any Linux that supports Gtk) and Microsoft Windows and allows you to send completely anonymous email to anyone anywhere.
While AnonyMail is not groundbreaking software, I wrote it because, as an activist, there are many times when I need to send mail quickly, easily, and anonymously. Most solutions, like TorMail, only meet one of those requirements and often require more work than it's worth just to send a single email. I hope AnonyMail addresses this and puts anonymity in the hands of the average user.
If you run Ubuntu, you can find it in the Software Center. Windows users can download it from here.