##QGIS Resources ##Maptime MSP - March 2015
Layer Blend Modes in QGIS Old, but relevant post
Blending Modes in Photoshop This is specific to Phtoshop, but illustrates how the common blend modes work
Color Impaired and Greyscale Previews Not available on OSX
GDAL/OGR You get these tools if you use the OSGeo4W or KyngChaos installers
Intro to GIS MOOC using QGIS not currently open
###Presentations on QGIS Gretchen Pederson - FOSS4G NA 2015