Source Wireframe Kit - Library of 537 blocks for desktop and mobile prototyping
Pano2VR - Pano2VR is a powerful software that enables users to transform their panoramic photos and videos into interactive virtual tours.
Form Wireframe Kit by InVision - A free wireframe kit from InVision
Krpano - Krpano is a panorama viewer and a virtual tour solution that allows the users to show all kinds of panoramic images on various platforms.
iOS Wireframing UX Kit - An easy, speedy way to wireframe for iOS
Kuula - Kuula is a platform that enables users to create, edit, and share 360-degree virtual tours.