You can get the list of data sets in a Socrata domain with the data.json route, for example; "http://soda.demo.socrata.com/data.json".
However there are some very nested objects that are inconvenient for R. This is just an example of how to flatten specifically the data.json return value from Socrata.
This is not tested. This was a demo in conjunction with work on ls.socrata in the package https://github.com/Chicago/RSocrata/