The following free resources are from Openstax.org.
Principles of economics
Principles of microeconomics
Principles of Macroeconomics
Concepts of Biology
Microbiology
Business Ethics
Chemistry
Chemistry: Atoms first
Organic Chemistry
Calculus (Volume 1)
Calculus (Volume 2)
Calculus (Volume3)
Introduction to Python Programming
Writing Guide with handbook
Introduction to Philosophy
World History (Volume 1)
World History (Volume 2)
Principles of management
Management Principles
Introduction to Business
Introductory Business Statistics
Organizational behavior
Principles of Accounting: Financial Accounting (Volume 1)
Principles of Accounting: Managerial Accounting (Volume 2)
Principles of Finance
Principles of Management
College Physics
College Physics 2
Physics (High School)
University Physics (Volume 1)
University Physics (Volume 2)
University Physics (Volume 3)
Precalculus
Precalculus: an investigation of functions
Precalculus: College algebra and trigonometry
SOCIAL SCIENCES
Introduction to Anthropology
Introduction to Sociology
Introduction to Psychology
Statistics