Apple has released a seed update to the last released build of Mac OS X 10.5 Leopard. Apple unleashed build 9A599 to developers 10 days ago.
The 9A557/9A559 Seed Update includes fixes to wireless networking and RAW image viewing in the latest development build of Mac OS X Leopard. The update is also being used to test new features with in the Software Update mechanism itself.
Apple is widely expected to declare a build in the near future suitable for Golden Master.