There are a few good ones around:

• Orfeo Toolbox
• [GRASS] 2
• [SAGA GIS] 3

All with the bonus of being able to be used though the QGIS interface using the SEXTANTE plugin like so http://blog.orfeo-toolbox.org/uncategorized/otb-inside-sextante-inside-qgis

There are a few good ones around:

• Orfeo Toolbox
• [GRASS] 2
• [SAGA GIS] 3

All with the bonus of being able to be used though the QGIS interface using the SEXTANTE plugin like so http://blog.orfeo-toolbox.org/uncategorized/otb-inside-sextante-inside-qgis