Free Data sets for machine learning practice
There are many places data sets are available for free, I have collected following links over the periods, many of them for learning purpose, there are few for real serious for problem solving.
UCI have famous data repository at http://archive.ics.uci.edu/ml/
Very good weather data at for at http://www.knmi.nl/climatology/daily_data/download.html
Data set for different ML problems order in terms of complexity http://college.cengage.com/mathematics/brase/understandable_statistics/7e/students/datasets/slr/frames/frame.html
If you have Wolfarm Alpha pro account, you can download research data in CSV format. For example (Hover your mouse on the plots to get download link) http://www.wolframalpha.com/input/?i=home+prices+folsom+california...