Apple has released Mac OS X 10.6.5 for Snow Leopard today. For a full list of fixes, updates, and additions, see the links below.
Some of the Mac OS X 10.6.5 highlights
* Addresses performance of some image-processing operations in iPhoto and Aperture.
* Addresses stability and performance of graphics applications and games.
* Resolves a delay between print jobs.
* Improves Bluetooth pairing with Magic Trackpad.
* Improves reliability of Ethernet connections.
* Adds RAW image compatibility for additional digital cameras.
* Security improvements (see link below)
* Full Apple Support Article
* Security updates found in 10.6.5
As always, you should back up your system, preferably through Time Machine if you have the capability, before installing the update.
The quickest/easiest way to get it, is through the Software Update feature available through the Apple (?) menu.