Horos - A free, open source 64-bit DICOM medical image viewer
errProof - The website has a lot of useful and unique tools.
Weasis - Weasis is a multipurpose standalone and web-based DICOM viewer.
Getcalc - getcalc.com - online calculators, formulas & work with steps (step by step calculation) for expressions, statistics, probability, finance, health, geometry, general purpose & engineering calculations along with basic & scientific calculators.
3D Slicer - Slicer is a community platform created for the purpose of subject specific image analysis and...
Insect - High precision scientific calculator with full support for physical units.