I'm glad to annouce that geobr is now officially available on CRAN. Here and here are quick intros on how to use geobr to get easy and quick access to shape files and other official spatial data sets of Brazil. The package currently includes several data sets for various years such as states, regions, municipalities, census tracts, statistical grid and others. The github repository is this, in case you want to keep track of the latest developments.
The package was developed by my team and I at the Institute for Applied Economic Research (Ipea). We are constantly working to expand and improve the package, so if you have any suggestions/contributions, please feel free to open an issue on Github.