I've installed a new module that tracks how many people you have referred to the site and ads a box on the registration page to allow those signing up to put in the user id of the member who referred them.

To get your referral link click the Profile link on the menu bar and you'll see a referrals section about half way down the page (see attached screenshot). So when you tell people about the site or post a link somewhere you can use this referral link so the site can keep track of how many people you have referred.

If you have any questions let me know.

Cheers!
~TheNerd