Advice for learning R after intro university class

Hello, I just finished my first R course at the University and want to continue to learn. Do any of you have advice for a low cost way to continue practicing in an orderly manner? Thanks!

Nothing beats working with real data. Two good sources are UCI Machine Learning Lab and Kaggle. Practice downloading, data cleaning, exploratory data analysis and descriptive statistics and then coming up with questions that you don’t know have been asked before and do a study.