Due to the shutdown of the federal government, it appears that many federal websites are down as well, including the Census API (see http://outage.census.gov/closed.txt). As a result, the acs.R package is currently unable to download data – sorry! If you to use acs.fetch or anything related that requires the API, you will probably get the following error:
> acs.fetch(geo=geo.make(state=25), table.number="B01003") Error in file(file, "rt") : cannot open the connection
I assume that once this all gets sorted out, the site will come right back as before.