Anyone that happens to launch Software Update today will be greeted by a new Java Update. Java Update 5 for Snow Leopard and Java Update 10 for Leopard.

Java Update 5 for Snow Leopard addresses the following issues:
Java for Mac OS X 10.6 Update 5 delivers improved compatibility, security, and reliability by updating Java SE 6 to 1.6.0_26.

Java Update 10 for Leopard adresses the following issues:
Java for Mac OS X 10.5 Update 10 delivers improved compatibility, security, and reliability by updating J2SE 5.0 to 1.5.0_30, and updating Java SE 6 to 1.6.0_26 for 64-bit capable Intel-based Macs.

J2SE 1.4.2 is no longer being updated to fix bugs or security issues and remains disabled by default in this update.

Unlike other Platforms Apple releases its own runtime for Mac OSX. However Apple is calling Java deprecated and won't allow it in the Mac App Store. Besides this Apple also announced it will stop releasing its own version of the runtime on the Mac platform and will be handing those 'keys' over to Oracle.

Java on Mac has been slow with updating compared to other platforms, so this could be a good thing in the longterm. Sadly it does mean the Java runtime won't come preinstalled on OSX Lion and higher.