YesGraph - Boost viral growth by recommending who users should invite
Viral Loops - Viral Loops is a viral and referral marketing platform to launch ranking competitions, sweepstakes, pre-launch and referral programs.
NewsWhip - Chrome extension that checks how viral your content is
Best Referral Programs - A curated directory of startup referral programs
Promo Self Serve - Launch a promotion across the internet in 90 Seconds
GrowSurf - Referral software for B2C, FinTech, and SaaS companies.