Apple Support:

The 10.6.5 Update is recommended for all users running Mac OS X Snow Leopard and includes general operating system fixes that enhance the stability, compatibility, and security of your Mac, including fixes that:

– improve reliability with Microsoft Exchange servers
– address performance of some image-processing operations in iPhoto and Aperture
– address stability and performance of graphics applications and games
– resolve a delay between print jobs
– address a printing issue for some HP printers connected to an AirPort Extreme
– resolve an issue when dragging contacts from Address Book to iCal
– address an issue where dragging an item from a stack causes the Dock to not automatically hide
– resolve an issue with Wikipedia information not displaying correctly in Dictionary
– improve performance of MainStage on certain Mac systems
– resolve spacing issues with OpenType fonts
– improve reliability with some Bluetooth braille displays
– resolve a VoiceOver issue when browsing some web sites with Safari 5

For detailed information on this update, please visit this website: http://support.apple.com/kb/HT4250

For information on the security content of this update, please visit: http://support.apple.com/kb/HT122

As always, you can download and install this update using Software Update on any Mac running OS X 10.6 Snow Leopard.