As of the January 2014 update to Photoshop CC, exporting to Sketchfab is natively integrated! If you purchase or upgrade to the latest version, you can already upload your models directly from Photoshop.
How to use
Open your 3D model in Photoshop.
Go to 3D → Share 3D Layer on Sketchfab...
Enter a title, description, tags and your API token, and mark it as
Private if necessary.
When the upload is complete, you can view your model on Sketchfab, adjust rendering settings, and save the default view.