SkyPaint

SkyPaint is a paint tool for creating and editing 3D, seamless, 360° panoramic images.
Using SkyPaint is simple: start with a pre-defined template or an initial backdrop.

Use the arrow buttons in the SkyPaint window to look around 'inside' the backdrop; when you see something you want to change, just press the "Paint This View" icon to transfer control to Photoshop (or almost any of the other popular paint programs).
After making changes to that part of the backdrop, use plugin commands to transfer the changes to SkyPaint and either save the panorama or continue editing by selecting and changing another part of the backdrop.