From the descriptions in Software Update:
- AirPort Utility Software Update 2009-0001 (version 5.4.1): a 19.5MB download
This update includes general fixes and compatibility updates for the following applications: AirPort Utility and AirPort Base Station Agent, including AirPort Disk Utility for Tiger. - iLife Support (version 9.0.1): a 52.3MB download
This update improves overall stability and addresses a number of other minor issues. It is recommended for all users of Aperture, iLife ’09, and iWork ’09. - AirPort Client Update 2009-001 (version 1.0): a 1.8MB download
This update is recommended for all Intel-based Macintosh computers running Mac OS X 10.5.6. It addresses issues with roaming and network selection in dual-band environments. - iPhoto Update (version 8.0.1): a 13.6MB download
This update improves overall stability and addresses minor issues in a number of areas, including internet connectivity, keyword import, and slideshow export.
You can find all four updates in Software Update.