Google Tag Manager is a tag management system (TMS) that allows you to quickly and easily update measurement codes and related code fragments collectively known as tags on your website or mobile app.
Open Graph is a protocol that is used to integrate any web page into the social graph.
Rewardful is a way for SaaS companies to setup affiliate and referral programs with Stripe.
Wistia is designed exclusively to serve companies using video on their websites for marketing, support, and sales.