BusyCal

A highly-customizable alternative to Apple's Calendar app with an extensive feature set, including OmniFocus integration.

PopClip

Select text in any Mac app and PopClip pops up with instant text actions. Install the OmniFocus extension and you'll be able to send selected text to OmniFocus.

Focus by Meaningful Things

Focus is a flexible productivity timer with built-in support for OmniFocus. Define your work in OmniFocus and use Focus to help you bring it to fruition.

Craft

Craft is a meticulously-designed note-taking app for iPhone, iPad, Mac, Windows and Web. It's well integrated with OmniFocus and is a great place for reference information and project support notes, whether you're using it individually or as part of a team.

Hookmark

Hookmark for macOS makes it possible to link your OmniFocus projects and actions to almost anything, including files, folders, notes, websites, and emails. Having what you need within easy reach accelerates the process of getting things done.

DEVONthink

DEVONthink is a powerful data storage and research app for Mac, iPhone, and iPad that's a natural complement to OmniFocus. Through the use of links, you can have a vast amount of data at your fingertips as you work on tasks in OmniFocus.

Spark Mail

A polished email client with a focus on email prioritization. Spark Mail also has innovative support for teams and integration with OmniFocus.

Airmail

An email client that allows you to create OmniFocus actions that reference emails, manually or automatically using rules.

Postbox

An email client for Mac and Windows that's speedy, customizable, and extensible. The Mac version includes native support for OmniFocus.

MindNode

Allows you to create visual outlines of your ideas and responsibilities. Useful when designing your system and for planning projects.

Mailplane

An email client that combines Gmail's web interface with a slew of additional features, including integration with OmniFocus.

Launch Center Pro

Launch Center Pro can be configured to provide quick and convenient ways to create and access OmniFocus tasks on iPhone and iPad.

IFTTT

IFTTT (If This Then That) is a web-based service that can be used to automatically trigger the creation of OmniFocus actions based on a wide range of conditions.

Fantastical

An alternative to Apple's Calendar app that provides enhanced functionality, a natural language interface, and OmniFocus integration.

TaskClone

TaskClone automates the process of adding Evernote, OneNote and Notion tasks to OmniFocus.

Drafts

Quickly and conveniently and capture text and then send it to OmniFocus and other destinations through the use of flexible, customizable actions.