Drupal modules to display external RSS feed
Feeds (previously FeedsAPI) is the one you want. Here is a quote about it (from the module's project page):

Import or aggregate data as nodes, users, taxonomy terms or simple database records.

One-off imports and periodic aggregation of content
Import or aggregate RSS/Atom feeds
Import or aggregate CSV files
Import or aggregate OPML files
PubSubHubbub support
Create nodes, users, taxonomy terms or simple database records from import
Extensible to import any other kind of content
Granular mapping of input elements to Drupal content elements
Exportable configurations
Batched import for large files