Anonymous Email and Remailer Services
WILL SELF-DESTRUCT - Anonymous Self-Destructing Email Service
WILL SELF-DESTRUCT makes it really easy to send email messages that can only be viewed for a certain time, and you can remain anonymous to boot.
AnonymousSpeech: Send Anonymous Email
Mail sent via AnonymousSpeech contains no traces to the sender, though you can even receive replies.
Private Critic - Anonymous Email Service
Private Critic lets you send, anonymously, praise and, well, helpful suggestions to others — office colleagues, for example. (Thankfully, anybody can prevent Private Critic to accept anonymous messages for their email address.)