An email client that allows you to create OmniFocus actions that reference emails, manually or automatically using rules.
An email client that combines Gmail's web interface with a slew of additional features, including integration with OmniFocus.
An email client for Mac and Windows that's speedy, customizable, and extensible. The Mac version includes native support for OmniFocus.
A web-based service that helps you tame your email and that reduces the need to create and manage Waiting items in OmniFocus.