Penn State offers a wide variety of free online classes (for no course credit). You can take a look at the Penn State Online Geospatial Education Program Class Calendar. From there you may want to take a look at:
Geog 883: Remote Sensing and Image Analysis and Applications: An intermediate-level course focusing on the use of remotely sensed imagery in geospatial applications. This course assumes that students have prior knowledge and experience in the basics of remote sensing, mapping, and GIS. Students who successfully complete GEOG 883 will be able to apply knowledge about remote sensing systems, processing of remotely sensed data, and derived data products to a variety of GIS application scenarios. They will be able to describe methods used to classify and analyze these data using commercially available software tools. Finally, students will each develop a final project of their own design, demonstrating their ability to apply their new skills to a real-world situation of personal or professional interest.
Geog 497D: Lidar Technology and Applications: An introduction to the capabilities of lidar sensors and platforms, data processing systems, and derived digital data products. Students in this course will master basic skills needed to leverage commercial lidar data sources and information products in a broad range of applications, including topographic mapping, flood inundation studies, vegetation analysis, and 3D modeling of urban infrastructure.
Lidar (Light Detection and Ranging) is an optical remote sensing technology that uses laser pulses to determine distance between the sensor and a surface or object. In the last 10 years, lidar has emerged as one of most important sources of data for topographic mapping, vegetation analysis, and 3D modeling of urban infrastructure. Federal, state, and local government agencies are acquiring lidar data and derived products for use in floodplain mapping, transportation planning and design, resource and environmental management, law enforcement, and emergency response. Much of this data is freely available to the public, and new uses for the data are emerging at a rapid pace. A thorough understanding of lidar technology and its application in GIS is part of the essential body of knowledge for today’s geospatial professional.
GEOG 480 - Exploring Imagery and Elevation Data in GIS Applications:An introductory level course focusing on the use of remotely sensed imagery and elevation data in GIS applications. GEOG 497G is an elective course in the Postbaccalaureate Certificate and Master of Geographic Information Systems (MGIS) degree programs. Students enrolling in Geography 497G should have a solid conceptual foundation in geospatial information science and technology (equivalent to Geog 482). Geography 497G is appropriate for those who are entering into the geospatial profession and wish to use imagery and elevation data in visualization and spatial analysis. Students who complete Geography 497G can advance their knowledge further by taking either Geography 497D or Geography 883.
when you are on the landing pages of each respective course, eg. GEOG 883, you can click on Course Outline, on the left hand side of the webpage, and begin the lessons.
I would also suggest taking a look at CLASLITE through Stanford Online as you get a software package that will familiarize you with techniques used in forest monitoring.
and if you are really ambitious, I would suggest exploring PCI Geomatica and downloading a Free Trial of PCI Geomatica 2013. There are Tutorials available through the PCI Geomatica website.