Relevant page in the Drupal Handbooks:

Aggregator: syndicating content

Introduction

RSS feeds and other formats of content syndication have been talked about a lot in the library world especially how it is part of a Web 2.0 information environment. You can easily find articles on what is RSS and such but I have yet to find some instructions on how I can use it for certain library functions. Perhaps people who write about Web 2.0 tools assume anyone can put two and two together and go forth and apply such new tools. But I haven't really understood these technologies until I started using them to build useful resources such as an alert service. The following sections will cover tasks related to subscribing content from external sources using Drupal's aggregator module.