Mac OS X 10.6 "Snow Leopard" hasn't been out for long, but Apple has already released an update for it, version 10.6.1.
Apple says the 10.6.1 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 for:
compatibility with some Sierra Wireless 3G modems
an issue that might cause DVD playback to stop unexpectedly
some printer compatibility drivers not appearing properly in the add printer browser
an issue that might make it difficult to remove an item from the Dock
instances where automatic account setup in Mail might not work
an issue where pressing cmd-opt-t in Mail brings up the special characters menu instead of moving a message
Motion 4 becoming unresponsive
To get the 10.6.1 update, use Apple's Software Update utility.