1. Google Dataset Search: Google Dataset Search is a valuable tool for researchers, data scientists, and enthusiasts in the field of machine learning and data analysis. This service, accessible at https://datasetsearch.research.google.com/, is designed to simplify the process of discovering datasets from a wide range of domains.
2. Kaggle: Kaggle is a well-known platform that hosts data science competitions and many other datasets. Find datasets in different domains and participate in competitions utilizing your machine learning skills.
3. UCI Machine Learning Repository: The University of California, Irvine maintains a repository where you can get datasets for machine learning projects. These are available for free and cover a wide range of topics.
4. Government and NGO Websites: Social, economic, and environmental issues are often covered by government institutions and NGOs datasets; examples include data.gov, World Bank Data or UNICEF Data.
5. Open Data Platforms: Some countries and cities have open data platforms where they share information related to public services (e.g., transportation), health among others. Seek out open data initiatives in your area.
6. GitHub: Many researchers and organizations use GitHub to share their dataset collections. You may look for repositories with datasets or go directly into repositories specializing in machine learning datasets.
7. Machine Learning Competitions Platforms: Some other platforms that run machine learning contests besides Kaggle are DrivenData or CrowdANALYTIX where you can also get the respective competition’s dataset.
8. Academic Databases: Academic institutions often provide research-related data sets. Check university websites, especially those relating to data science and ML departments.
9. Social Media APIs: APIs from social media sites such as Twitter, Facebook and Instagram enable access to public data feeds. Note that there terms of service as well as privacy regulations guiding how social media data should be used should be followed strictly.
10. Synthetic Data Generators: In some cases synthetic data generators can be used to create artificial datasets for testing purposes or experimentation only with regards to this matter.