RSSme - RSSme is free, lightweight and user-friendly RSS editor.
MarsEdit - MarsEdit is a desktop blog editing application for the Mac. It provides an offline interface to most popular blogging systems. WordPress, Blogger, Tumblr, Movable Type, and many other systems are supported.
Feed Launch .NET - Feed Launch .NET is an open-source feed editor for RSS 2.0 and ATOM 1.0 Feeds.
Drivel - Drivel is a GNOME client for working with online journals, also known as weblogs or simply...
Feeder by Reinvented Software - Feeder is for creating, editing and publishing RSS feeds on macOS.
Desk - An award-winning & beloved desktop publishing client, exclusively for OS X.