Free PowerPoint training resources are available at Support.Office.com, SkilledUp and GCFLearnFree.org, as of 2015. Additional sources for free training courses and tutorials include BrightCarbon and Computer-PDF.com.
Support.Office.com is an official Microsoft Office training center. Microsoft provides training courses and quick-start guides for all Office applications and services, including PowerPoint, Excel, Word and Access. The website categorizes the tutorials by application and scenario.
SkilledUp is an online resource that provides software training solutions for small, medium and large organizations. The website features an article that outlines 40 PowerPoint resources and tutorials. However, not all the resources mentioned are free of charge.