Resources

Project management standards
PMBOK® Guide, Project Management Institute (PMI)
International Competence Baseline, International Project Management Association (IPMA)
Scrum Guides
PRINCE2® certifications, PeopleCert

Open-source software
Project management (alternatives to Microsoft Project): Gantt Project, ProjectLibre
Mind mapping (alternative to Xmind, MindManager): Freeplane
Diagrams and flowcharts (alternative to Microsoft Visio): draw.io

Professional publications
International Journal of Project Management (academic journal, English)
Project Management Journal (academic journal, English)
Projektmagazin (professional portal, German)