ObsidianObsidian is a highly-adaptable note-taking app. Notes are stored in Markdown text files in the location of your choice and it's free for personal use.
NotionA highly-flexible, cloud-based app that individuals and teams can use to write, plan, collaborate, and get organized.
Spark Mail A polished email client with a focus on email prioritization. Spark Mail also has innovative support for teams and integration with OmniFocus.
EvernoteEvernote is a natural complement to OmniFocus. Use it to store ideas for upcoming projects and as a repository for project reference material.
