For those of you who are not familiar with Kaggle.com, the latter website is a competition website concerned with data science and Machine Learning problems. Several commercial and non-profit companies and organization make their problems open to the public domain in hopes that they can find solutions to their own data problems or improve the performance of their existing ones.
No matter what your level of expertise is with machine learning, there are many beginner-level problems to learn from and solve. There are also several real-world competitive problems that if solved efficiently would grant the winner teams up to 100,000$ as well as reputation points on the leaderboard. It is also a great source for learning machine learning approaches to solving problems. For more information on kaggle, I suggest browsing their homepage for more details.