Mac OS X 10.5.6 Update

Apple released Mac OS X 10.5.6 Update which “Includes general operating system fixes that enhance the stability, compatibility and security of your Mac”. The update include many fixes including the following:

Various improvements to performance and stability in Mail.app, iCal, Airport and Safari
Graphical improvements
DVD player performance improvements
A new Trackpad panel in System Preferences for portable Macs
Time Machine and MobileMe improvements
Other various fixes.

You can install the update using the Apple Software Update or downloading it directly from Apple’s website.
Via TUAW.