What is Letter To A Stranger
Letter To A Stranger is most easily described as Chattroulette for email.
You can participate by sending an email in, which will then be (semi)randomly distributed out to another user.
They then write you a reply, earning them kudo's and you a response. You can keep the thread going as long as you both want to.
If they wait too long on the first reply, the email goes stale and is passed along to another user.
Everything is kept psuedo-anonymous. No one can get your real email address unless you give it to them (which you shouldn't, by the way).
Where do I sign up?
You don't, it's not ready yet.