Is there an easy way to download the set of census blocks (12-digit FIPS codes) for a given state? I've tried using R packages tigris and acs to no avail. (Well, tigris works but it gives me the shape data for block which is major overkill since I only want to know what blocks are defined for each state.)
This isn't really a R-specific answer, but you can download a flat .csv for any given state at the FCC's website: https://www.fcc.gov/general/census-blocks-state
You might want to check out NHGIS. You can download census block data and shapefiles for multiple years.
If you are only interested in administrative boundaries of Census Blocks, there are 3 options to download Census Block shapefiles from the Census Bureau's pages (Option 1, Option 2, Option 3). Option 1 is their www2 version which is easier to navigate in a web browser, and option 2/3 are choices that can be used through an FTP program such as FileZilla.
I'll give a brief in description of the file names:
The YYYY stands for the year in which the boundaries apply. The SS is the 2-Digit FIPS code for the state in which the Census Blocks are located. The DD stands for the decade in which the Census Block geographical boundaries were created/edited. Finally, tabblock stands for tabulated block.