Photosynth.net is host to both photosynths and panoramas.
Originally, in 2006 - early 2010, there were only photosynths and the site used a Direct3D hardware-accelerated viewer as a plugin that only supported Internet Explorer on Windows and Firefox 2 or 3 on Windows.
In early 2009, the Photosynth team changed the default photosynth viewer on the site to a Silverlight app which worked for all browsers on Windows and Mac. It only had access to the CPU, so ran more slowly than the Direct3D viewer, since Silverlight 2 - 4 did not have free access to the GPU.
In early 2010, panorama support was added to the site and the ICE/HDView team in Microsoft Research helped write a panorama viewer in Silverlight to view ICE panoramas.
In early 2011, Photosynth's mobile panorama app launched on iOS, with Windows Phone 7 following in 2012 and Windows Phone 8 following in 2013, but none of the mobile apps support creating or viewing photosynths.