InviteRobot - Instant subscription for paid Slack communities
Usersnap - Visual Feedback - Usersnap helps your business with its versatile feedback platform to build better, more successful products and services with the help of user feedback. Collect feedback along your product development lifecycle. Try it for free.
SlackPass - Subscription access to anything with Slack
BeFrank - Feedback platform for graphic designers
Grapevine Surveys - Grapevine is an online survey tool for employee surveys.
Marvel - Turn sketches, mockups and designs into web, iPhone, iOS, Android and Apple Watch app prototypes.