There is lots of great content and services available through web services, or even page scrapping. However web services all have different architectures (SOAP, XML-RPC, REST, etc) and authentication schemes (HTTP-Basic, OAuth, etc) which makes them a pain to include in your Drupal site.
Yahoo! offers a service called YQL which allows you to access lots of web services or even scrape web pages using a syntax like SQL. This makes it really easy to access web data and include it in your Drupal site.
