R has lots of built in example data sets

The package datasets contains a selection of example datasets which can be used for testing out and playing with R functions.

You can get a list of all available datasets by running data() in a console. Each dataset is available by default in a variable the name of which is outputted in data(), e.g. AirPassengers or cars.

A summary of the data can be generated using the R function summary, e.g. summary(cars).