The latest update to Leopard is available now. What do you get with the  nearly 200 MB update? Airport and network fixes, Time Machine, Time Capsule  and Spaces updates, and of course, Apple includes the usual spiel;

"The Mac OS X 10.5.3 Update is recommended for Mac OS X 10.5, 10.5.1, and 10.5.2 Leopard. It includes general operating system improvements that enhance the stability, compatibility, and security of your Mac."

Remember everyone, updates should always follow a back up of important data.