Points

Initial settings:

From admin/settings/userpoints

You get points for:

referring

posting to a blog

posting to a poll

posting a book review

posting a comment

moderating a comment

giving a kudo

all the above get one point

IF a user registers, they get 5 points.

At 50 points you get an email.  You can change the text in this email (edit-userpoints-email-text)