The InterSystems Learning Website has many important iterative courses. So if you want to learn about InterSystems and start to work with InterSystems this is the path:

Overview:

• Introduction to InterSystems Products and Technologies: https://learning.intersystems.com/course/view.php?id=1168&ssoPass=1

Fundamentals:

• InterSystems ObjectScript Basics: https://learning.intersystems.com/course/view.php?id=959&ssoPass=1
• InterSystems SQL Overview: https://learning.intersystems.com/course/view.php?id=960&ssoPass=1
• InterSystems IRIS Objects Introduction: https://learning.intersystems.com/course/view.php?id=938&ssoPass=1
• Migrate to IRIS (contribution from Kristina Lauer): https://learning.intersystems.com/course/view.php?name=MigratingToIRIS

Backend Development:

• Setting Up RESTful Services: https://learning.intersystems.com/course/view.php?id=1298&ssoPass=1
• Using JSON in InterSystems IRIS: https://learning.intersystems.com/course/view.php?id=972&ssoPass=1
• Hands-On with InterSystems API Manager for Developers: https://learning.intersystems.com/course/view.php?id=1747&ssoPass=1
• Building Data-Driven Web Apps: https://learning.intersystems.com/course/view.php?id=1237&ssoPass=1

Integration Development:

• Integration Architecture: https://learning.intersystems.com/course/view.php?id=908&ssoPass=1
• Building BPL Business Processes: https://learning.intersystems.com/course/view.php?id=1290&ssoPass=1
• Building Custom Business Operations: https://learning.intersystems.com/course/view.php?id=1288&ssoPass=1
• Building Custom Business Services: https://learning.intersystems.com/course/view.php?id=1291&ssoPass=1
• Data Transformations Basics: https://learning.intersystems.com/course/view.php?id=1170&ssoPass=1
• Very nice external resource: https://github.com/grongierisc/formation-template
• Interoperability Course (contribution from @guillaume Rongier): https://community.intersystems.com/post/ensemble-interoperability-traini...

Analytics Development:

• IRIS BI Architect: https://learning.intersystems.com/course/view.php?id=1752&ssoPass=1
• IRIS BI Analyzer: https://learning.intersystems.com/course/view.php?id=1793&ssoPass=1
• BI Data Models: https://learning.intersystems.com/course/view.php?id=1796&ssoPass=1
• InterSystems IRIS Adaptive Analytics Essentials: https://learning.intersystems.com/course/view.php?id=1715&ssoPass=1
• Getting Started with InterSystems Reports: https://learning.intersystems.com/course/view.php?id=1538&ssoPass=1
• Hands-On with IntegratedML: https://learning.intersystems.com/course/view.php?id=1535&ssoPass=1 Paths from learning.intersystems.com (contribution from @jenny Ames)

If you're looking to get started, you can also personalize which paths you take based on what you're trying to do:

• Building a Server-Side Application with InterSystems: https://learning.intersystems.com/course/view.php?name=IRIS%20Server%20Side
• Building Business Integrations with InterSystems IRIS: https://learning.intersystems.com/course/view.php?name=InteroperabilityForBusiness
• Analyzing Data with InterSystems IRIS BI: https://learning.intersystems.com/course/view.php?name=BuildingAnalyzer
• Build Data Models Using Adaptive Analytics: https://learning.intersystems.com/course/view.php?name=AALP
• Delivering Data Visually with InterSystems Reports: https://learning.intersystems.com/course/view.php?name=InterSystemsReports
• Predicting Outcomes with IntegratedML in InterSystems IRIS: https://learning.intersystems.com/course/view.php?name=Learn%20IntegratedML

Alternately, there are a several larger paths for implementation partners (or others who will be doing everything, paths are open to all) here: https://learning.intersystems.com/course/view.php?name=IPLPs