Apple has just released the latest minor update to Mac OS X 10.5 a.k.a. “Leopard”. Tagged as version 10.5.7 it includes various general OS fixes as well as updates to iCal, Mail, Parental Controls and Printing.
The update is available via Software Update in the Apple menu or, our preferred method, by downloading the 10.5.7 Combo Updater.
Also available via Software Update is Safari 3.2.3 as well as Security Update 2009-002 for Mac OS X 10.4 “Tiger”.
[ADDED 2009-05-13 10am]
It appears a few upgraders, myself included (see the first comment,) are experiencing problems with the 10.5.7 update including stuck in the blue startup screen (what happened to me) as well as loss of some of the previous screen resolutions. No idea how widespread these problems may be so make sure your important files have been backed up and you might want to consider waiting for the dust to settle before upgrading mission critical machines.
FYI: I upgraded three Macs, two Intel and one PowerPC, all using the Combo Updater and experienced a problem on one of them.