Apple Mac OS X 10.6, known as Snow Leopard, will be released tomorrow, on August 28th 2009.
This is not a free upgrade for Mac users. USD 29 if you are trying to upgrade from Mac OS X 10.5 (Leopard). Or you can purchase Mac Box Set - a bundle of Mac OS X 10.6 + iLife 09 + iWork 09 for only USD 169 altogether.
Said to have speed and performance improvements, Snow Leopard doesn't come with a lot of new features. It introduces 64-bit computing to improve computer's CPU computational capability. Apart from this, many applications get enhancements, such as higher resolution video conference in iChat, faster backup using Time Machine, and newer version QuickTime X. A cool feature is introduced to allow Chinese character input using touchpad.
So, it's time for upgrading your OS X !