When you send an email to anyone, you have the chance to promote your website to them. This does NOT mean simply go around finding email addresses and spamming them with advertisements but instead, when you are emailing a friend, business partner or someone you know and are just having a chat with, you can add a link to your website at the bottom of the email.
This can work exceptionally well on ebay as when someone buys a product from you, you would normally have to exchange emails with them to tell them details about delivery methods and timing so when you email them about the transaction you can simply add a short description of your site and a link at the end of your emails. If you trade on ebay a lot, then you have the chance to gain many visitors.
You can also use this method when emailing your friends and work associates.Do not simply email people in order to advertise your site but instead use it as a casual method of advertising when you would normally be emailing people.