(Needs to make page more organized. My apology for messy arrangement.)
Esri Udemy Online Course: https://esri.udemy.com/
If someone is working on or interested in Global Information System and Remote Sensing, ESRI website, tutorials, online library and many other resource will definately makes learning easier. Also, Hexagon Spatial [http://www.hexagongeospatial.com/] is another wonderful site to learn about remote sensing and GIS. This link, http://fas.org/irp/imint/docs/rst/Front/tofc.html, will also be useful to learn about Remote Sensing and Image Processing.
Geotech Centre: http://www.geotechcenter.org/
Joshep Kherski (Geographer Specialist): http://www.josephkerski.com/
Kentucky Geographic Alliance:
Online Sources to Download Landsat Database:
USGS Glovis: http://glovis.usgs.gov/ (USGS Glovis is online database to download different images and other data related with remote sensing and GIS as well as related field.
These links provides quick guide and information about landsat project, Remote Sensing GIS and related issues:
http://landsatlook.usgs.gov/QuickGuide.html link provide quick guide how to download the landsat image data from landsatlook.
Landsat Science: http://landsat.gsfc.nasa.gov/
Path Row Finder: http://landsat.usgs.gov/tools_latlong.php
Digital Globe for high resolution Images: https://www.digitalglobe.com/