There are a few good open source Remote Sensing programs out there. One is Spring, out of Brazil. It integrates GIS and Remote Sensing. It is available in four languages, English, Portuguese, Spanish, and French. It comes with full documentation in the four languages. It runs on Windows or Linux or can work with data on a remote server. There are translators to move data files from Shapefiles, E00, MapInfo, and DBF into SPRING format.
The next one is eFOTO out of Brazil. The web pages are in English, Spanish, and Portuguese. It comes in versions for Windows, MacOS X and Linux. It has good documentation to learn the software and more about photogrammerty principles.
If you are processing ground scanning radar SAR (Synthetic Aperture Radar)data (not to be confused with WSR-88D Dual Pol weather radar data), a good program is RAT out of Germany. There are versions for Linux, UNIX/IRIX, MacOS X, and can be adapted to run on Windows.
Another SAR processing program is PolSARpro. It has versions for Windows, Linux, Unix/Solaris, and MacOS X. It is made available from the European Space Agency and has developers around the world. It also has full training courses on the webpage to learn more about the software and SAR in general.
One more is MultiSpec from Purdue University for analyzing multi-and hyperspectral imagery. It is available for Windows and MacOS X.
The US Army Corps of Engineers has HyperCube, another tool for analyzing multispectral and hyperspectral imagery. It is available for Windows and MacOS X.
A last imagery interpretation program is Opticks. It is available for Windows, Linux, and Solaris SPARC UNIX.
There are more open source GIS programs out there, so go to OSGeo.org and search and look for what you find interesting to use in professional development and your workflows.