Leak is an anonymous email service that lets you send email messages to people without revealing your identity. All you have to do is visit Leak and fill in the person's email address, state your relationship type and hit send. You message drops on the person's email box---they will never find out you are the one that sent in the email.
Leak is still very young and for that, you can't send your secret message along with attachments.
I just made a visit to Leak's website and I found out it is down at the moment due to its ''fast'' popularity(That goes to show that people loved this service). It announced yesterday on its Twitter handle that it broke its daily record of leak sent in one day---11,5k+. Go the website here
A word of advice, be careful how you use the service.