Apple today released Security Update 2009-001 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 2009-001 is available via Software Update and also as standalone installers.
More info and download links: http://support.apple.com/downloads/
For information on the security content of this update, visit: http://support.apple.com/kb/HT3438