Apple has released their first update to Mac OS X Leopard (10.5.1) today:

The 10.5.1 Update is recommended for all users running Mac OS X Leopard and includes general operating system fixes that enhance the stability, compatibility and security of your Mac.

Apple details the improvements in this technote. Some highlights include:

- Allows password-protected accounts on AirPort Disks to show up on in the Finder’s Shared Sidebar.
- Addresses formatting issues with certain drives used with Time Machine
- Addresses a potential data loss issue when moving files across partitions in the Finder.
- Improves the reliability of Back to My Mac-enabled Macs appearing in the Finder’s Shared Sidebar.

Source :  Apple.com