The new 2.81 Feature -> Option: Affect Only Origins - User Feedback - Developer Forum
How to rotate Pivot point - User Feedback - Developer Forum
ArtStation - Free Pivot Painter addon for Blender
Blender Market - Pivot Transform helps you change the position of the pivot point as needed. You can align it to the normals of the desired polygon, rotate and move it, or
Pivot Painter for Blender - Community & Industry Discussion - Epic Developer Community Forums
New Addon and Blender tutorial: Quick Pivot Tools (free) - YouTube
Great Blender Addon for Concept Art | Simply Concept - InspirationTuts