Feather Attribution - A free and tiny javascript library to track UTM tags, ref and referrer data client side so you can store these in your own database.
Creddon - Tweet for a cause and a sponsor will donate $1 to charity
LoyalAs - Get and track referrals automatically.
Wheelys Dreams - Crowdfunding for making dreams become real
ToneDen Lasso - Put fan and customer acquisition on autopilot
eSolidar - Charity shops and online auctions to support great causes