Apple roll out the Mac OS X 10.6.3 update, to the operating system, which has reportedly been in beta since late December. The update includes more than 70 security fixes and 49 general improvements to Snow Leopard, including fixes for Mail, MobileMe, and AirPort. Snow Leopard users can simply choose "Software Update" from the Apple menu, and install the upgrade from there, or they can download the standalone update installer from Apple Support. Users updating their system through the Software Update installer should be warned that the file size may vary from computer-to-computer. Users not installing the upgrade through the Software Update installer can download the required files here.
More info: Release Note