GIS
DNR GPS – utility for easy transfer of GIS data to Garmin devices: www.dnr.state.mn.us/mis/gis/DNRGPS/DNRGPS.html
QGIS – Opensource GIS with GUI: www.qgis.org/en/site/forusers/download.html
SAGA GIS – Raster analysis www.saga-gis.org/
WhiteBox Tools: https://www.whiteboxgeo.com/
Remote Sensing
ESA SNAP – Powerful freeware for work with satellite imagery (especially Sentinel) step.esa.int/main/download/
Statistics
R Studio – powerful IDE for R, Opensource www.rstudio.com/
Fieldwork
Field-Map www.fieldmap.cz/
ODK Collect opendatakit.org/use/collect/