Top 20 free data science data sets with links

1. Iris Flowers: https://archive.ics.uci.edu/ml/datasets/Iris
2. Titanic: https://www.kaggle.com/c/titanic/data
3. Adult Income: https://archive.ics.uci.edu/ml/datasets/Adult
4. Wine Quality: https://archive.ics.uci.edu/ml/datasets/Wine+Quality
5. Boston Housing: https://archive.ics.uci.edu/ml/datasets/Housing
6. Student Performance: https://archive.ics.uci.edu/ml/datasets/Student+Performance
7. Breast Cancer Wisconsin: https://archive.ics.uci.edu/ml/datasets/Breast+Cancer+Wisconsin+(Diagnostic)
8. Black Friday: https://www.kaggle.com/mehdidag/black-friday
9. Pokemon: https://www.kaggle.com/abcsds/pokemon
10. FIFA 18: https://www.kaggle.com/thec03u5/fifa-18-demo-player-dataset
11. US Accidents: https://www.kaggle.com/sobhanmoosavi/us-accidents
12. IMDB Movies: https://www.kaggle.com/tmdb/tmdb-movie-metadata
13. Human Resources: https://www.kaggle.com/ludobenistant/hr-analytics
14. Twitter Sentiment Analysis: https://www.kaggle.com/kazanova/sentiment140
15. Car Evaluation: https://archive.ics.uci.edu/ml/datasets/Car+Evaluation
16. Air Quality: https://archive.ics.uci.edu/ml/datasets/Air+Quality
17. SMS Spam Collection: https://archive.ics.uci.edu/ml/datasets/SMS+Spam+Collection
18. Heart Disease: https://archive.ics.uci.edu/ml/datasets/Heart+Disease
19. Chicago Crime: https://data.cityofchicago.org/Public-Safety/Crimes-2001-to-present/ijzp-q8t2
20. NYC Taxi Trip: https://www1.nyc.gov/site/tlc/about/tlc-trip-record-data.page

Please note that these are just a few examples and there are many other free datasets available on the internet, these datasets may be updated or removed by their authors in the future, also you can use these datasets for educational and research purposes, but please read and follow the usage license of each dataset before use.