Recommended free software

QGIS 
- Geological mapping (Windows)
www.qgis.org

Oasis Montaj Viewer 
- Database management, gridding and map creation (Windows)
www.geosoft.com/support/downloads/viewers/oasis-montaj-viewer

Mag2dc and Grav2dc 
- Simple 2D magnetic and gravity modeling (Windows)
http://www.wits.ac.za/academic/science/geosciences/research/geophysics/gordoncooper/6511/software.html

Euler 
- Simple 2D Euler Deconvolution (Windows)
http://www.wits.ac.za/academic/science/geosciences/research/geophysics/gordoncooper/6511/software.html

Flex2D 
- Simple 2D flexure modelling (Mac)
http://www.ux.uis.no/~nestor/work/programs.html

3D Geophysical Modelling and Interpretation
http://patrick-cole.github.io/pygmi/

Python Geophysical Tools
http://www.agilegeoscience.com/blog/2015/7/29/introducing-bruges-1?utm_content=bufferd9242&utm_medium=social&utm_source=facebook.com&utm_campaign=buffer

GMT Geophysical Tools