Apple has released Security Update 2008-005 which is recommended for all users and improves the security of Mac OS X. Previous security updates have been incorporated into this security update.
Security Update 2008-005 is available via Software Update and also in a variety of standalone installers.
More info and download links:
• Security Update 2008-005 (Leopard) – 65MB
• Security Update 2008-005 (Intel) – 143MB
• Security Update 2008-005 (PPC) – 88MB
• Security Update 2008-005 Server (Intel) – 180MB
• Security Update 2008-005 Server (PPC) – 135MB
About Security Update 2008-005: http://support.apple.com/kb/HT2647