SP1 of Reporting Services can be downloaded from the following site:

http://www.microsoft.com/downloads/details.aspx?FamilyId=580FEBF7-2972-40E7-BCCF-6CD90AC2F464&displaylang=en

It contains the following new enhancements and fixes:

  • Excel rendering extension has been improved and now supports viewing in Excel 97 and 2000.
  • PDF rendering extension is more robust and has better performance.
  • Chart control provides more control over display styles.
  • References to external URLs (images and resources) from within a report are now supported.
  • Data caching behavior for report preview is now supported.
  • Newline in expressions is now supported.
  • The style of the HTML Viewer toolbar can now be modified through a style sheet.
  • New URL parameters offer more options for customizing report presentation at run time
  • Report Manager proxy persists authentication cookies so that they can be used by custom security extensions.
  • Hidden parameters are now supported.
  • Temporary snapshots can be compressed as well as stored on the file system.
  • Integrated security support for accessing report data sources can be disabled.

The Readme file is a good place to start to get the latest, in-depth info on the above improvements (okay, I know nobody reads the readme, but I'm a doc guy and I have to plug it, and it will seriously be worth your time if you are interested in any of the SP1 enhancements).