Referral Candy - Run a fully automated, customizable and easy to integrate referral program for ecommerce.
YesGraph - Boost viral growth by recommending who users should invite
Ambassador - Referral Automation, Made Simple.
NewsWhip - Chrome extension that checks how viral your content is
ReferralRocket.io - Referral Program Software for SaaS
Promo Self Serve - Launch a promotion across the internet in 90 Seconds