I know it's old-fashioned, but visiting bookstores in a new city is a great pleasure. Especially used bookstores. There's a fine one close by the conference hotel:
111 Mathewson St, Providence, RI - (401) 521-2665
There's also a first-rate scholarly bookstore:
240 Westminster St, Providence, RI - (401) 273-7900
A 25-minute or so hike through the Brown campus will take you to the Brown University Bookstore, newly renovated. An excellent selection, and a great coffee shop!