Captain Chords - Write chord progressions in your favorite DAW
Plugin Boutique - Inspirational MIDI effect that makes finding chords and progressions intuitive and fun
RapidComposer - MusicDevelopments RapidComposer: Music Prototyping and Automated Composition Software
Cthulhu - VST MIDI-FX plugin for harmonic inspiration
Instachord - MIDI Processing Plugin that helps you play chords and chord progressions faster and easier.
Helio Workstation - Cross-platform lightweight speed-painting tool for creating music.