Basically, any viewer that supports DICOM query/retrieve should be compatible with Orthanc.
Because the Orthanc project is focused on the promotion of free software for medical imaging, we do not publish the list of proprietary DICOM viewers that are compatible with Orthanc. Here is a list of free and open-source viewers that are known to be compatible with Orthanc (do not hesitate to warn us about other compatible FOSS):
Make also sure to check out the following extensions to Orthanc:
Very importantly, Marco Barnig independently keeps track of a list of Mobile DICOM Viewers that are compatible with Orthanc. The Orthanc project is very grateful to Marco for this great contribution.
As far as Sébastien Jodogne is concerned, he uses the Web viewer plugin and the ImageJ extension for simple analysis tasks. For more intensive 3D viewing, he uses Ginkgo CADx. Finally, for advanced usages (such as PET-CT fusion or contouring), he switches to 3D Slicer.
If you face problems when configuring DICOM networking, make sure to follow the troubleshooting guide.