Apple has released Mac OS X 10.6.3 v1.1, what is essentially an update to its recent update for Snow Leopard. It contains a typical round of stability, compatibility, and security fixes for Mac OS X, though apparently not enough to warrant a bump to 10.6.4.
Included in v1.1 of 10.6.3 are improvements to QuickTime X, OpenGL-based apps, coloring messages in Mail, and printing reliability. This update also resolves issues with opening files with some special characters in Rosetta apps, color problems with HD content in iMovie, recurring events in iCal when connected to an Exchange server, and it improves performance of Logic Pro 9 and Main Stage 2 under 64-bit mode. Apple digs into greater detail in its release notes.
Mac OS X 10.6.3 v1.1 weighs just over 785MB, but is strangely not available via Software Update. You can grab it as a Combo update from Apple’s support site.