You could always create a
mailing list using you current friends email addresses, and constantly
collecting emails as a requirement before you give away any freebies or free
ebook. With the mailing list, you could update the people who are in your list
with information about what is new in your website, give away further freebies
and any other marketing information. As long the people in the mailing list do
not opt to be out of the list, you could always provide them with information.
This will make people to come again and again to your website and even possibly
talk to others about your site.