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.
Twitter Polls - Polls embedded in tweets
LoyalAs - Get and track referrals automatically.
Simple Poll - The easiest way to create polls in Slack
ToneDen Lasso - Put fan and customer acquisition on autopilot
Curious Polls - Answer a question once a day for the chance to win £100/$100