Substack

TheirStack is a web-based market intelligence platform that identifies companies by their technology stacks and hiring signals. The service aggregates technical usage and recruiting data to help teams find and target prospects; the site states it tracks about 33,000 technologies and 231 million job postings.

Prosed is a web service that assembles newsletters, posts, and other content into a publish-ready book. It converts a creator's existing content and ideas into a formatted manuscript for publishing.

Beehiiv is a newsletter platform that provides tools to create, grow, and monetize email newsletters and accompanying websites. It includes subscriber management, analytics, monetization features, and templates to build newsletters and sites without coding.

Kit is an email-list platform used as a source from which an email list can be exported before importing it into another email platform.

ConvertKit is an email marketing platform and automation service aimed primarily at creators and small businesses. It provides tools for building email lists, creating landing pages and forms, automations, subscriber tagging and segmentation, and commerce features for selling digital products and subscriptions.