ParaView is a popular open source application for data analysis and visualization. OnScale results can be post-processed in ParaView, and over on his blog FEA for All, Cyprien Rusu has explained how!
Cyprien talks through the steps in the following video:
In brief, using OnScale Analyst you can export data files in ParaView .vtu format using the data form out prvu command. Check the Command Reference for more information about the syntax of this command.