A best way to get huge traffic to your site/blog is through facebook. To get traffic you need the visitors get subscribed to you. Offer them a free download with content locking, to unlock the content they must connect with your facebook app. This lets you to save their important details like their email, facebook id. Later when new post or downloads in your site can be easily informed to your subscribers through this content locking management script.
How it works :- You will provide two urls one is content url, other is survey url. If the user is connecting with facebook app for first time, after connecting with the app he will be taken to content url.
if the user already connected with the app he will be taken to survey url, where he needs to complete a survey to download the content.