Intro  -->  https://gephi.org/
Import SpreadSheet or Project 1  -->  https://gephi.org/gexf/format/datasets.html
Import SpreadSheet or Project 2  -->  http://www.sociopatterns.org/files/datasets/002/sp_data_school_day_1.gexf.zip
Plugins  -->  https://marketplace.gephi.org/plugins/