iCal
iCal is the Mac's built-in calendar applications. It's the easiest way to keep track of appointments, events, holidays and birthdays.
Spotlight Search
Mac OS X has a great built-it search function called Spotlight that helps you find any file on your Mac. Never loose an email or a document again!
Exposé
If you have many applications and windows open at the same time, it may be hard to find the right window. Using exposé your problems are solved.
System Preferences
Your Mac is full of settings that will help you configure it to better suit your needs. Just click System Preferences to get started.