Apple has released the latest OS X Mountain Lion version 10.8 yesterday, there are plenty of features that are included in new Mac OS X and the price which they have placed is very nominal i.e. $19.99 much less than the previous versions.
Some of the features include a new notification center, iMessages, new dictation, iCloud Synchronization of notes and reminders etc.
The below video can give you a detailed overview of the features which are most useful for a common user. In my opinion the video is a good tutorial as well for the pupils who are new to the Mac OS X Mountain Lion UI.