The RSS Specifications blog has an article listing 15 uses for RSS in an educational environment. While many of these items fit within a broader academic context, several could be easily ported to the library. For example, a library could use RSS to publish a study guide. It might be general (i.e., one word aimed at a certain reading level each day) or specific to a user group (daily historical facts for a specific K-12 or higher ed course).
How is your library using RSS to communicate with your community?