Right after releasing a major system update with the largest number of security fixes ever, Apple has released two other updates which contain security fixes.
iTunes 9.1, released in advance of the iPad, which will be available this Saturday, fixes seven bugs, but only one for Mac OS X (the others are for Windows). This update, for Mac OS X 10.4.11 or later, is available for download via Software Update, or from Apple's iTunes download page. It's about 93 MB. Full information about the security fixes is available here.
As for the QuickTime update, it fixes 16 bugs, and is available for Mac OS X 10.4 and 10.5 The fixes it contains were in the Mac OS X 10.6.3 update that was released on Monday. It, too, is available via Software Update, or from Apple's Downloads page, and full information is available here. It's a 69 MB download.