RafflePress - RafflePress is the best WordPress contest and giveaway plugin. Grow your email list, followers, and website traffic with viral giveaways in WordPress.
Thankbot - Drive more business with handwritten notes
UpViral - Referral marketing platform enables anyone in running effective and profitable viral marketing campaigns – in minutes.
Socialkeeper - Cultivate your friendships
Tremendous - Tremendous is a customer and employee loyalty platform that allows companies to reward their customers for surveys promotions and referrals.
Thankster - Automagically send hand written cards