edX is an American massive open online course (MOOC) provider created by Harvard and MIT. It hosts online university-level courses in a wide range of disciplines to a worldwide student body, including many courses at no charge.

Coursera works with universities and other organizations to offer online courses, certifications, and degrees in a variety of subjects. In 2021 it was estimated that about 150 universities offered more than 4,000 courses through Coursera.

MathWorld is an online extensive mathematics resource, where you can find intuitive and simple explanations of concepts from the fields of Probability Theory and Statistics, and mathematics in general.

Kaggle is an online community of data scientists and machine learning practitioners. Kaggle allows users to find and publish data sets, explore and build models in a web-based data-science environment, work with other data scientists and machine learning engineers, and enter competitions to solve data science challenges.

You can download for free open-source software of high quality, equivalent to popular statical packages (used for data and mathematical analysis, etc.). It is supported by the Organization of Free and Open-Source Software (FOSS).