The original contextual menu button is to hold down the control key and click--that goes back to the 90s and continues on today.
Since the prevalence of USB in the late 90s, Apple has supported most multi-button mice out of the box (though Apple's own Mighty Mouse often has its right click disabled until you visit System Preferences and set up your buttons).
In the last 4 years or so Apple has increasingly added functionality to the trackpad of its notebooks: two-finger scrolling (horizontal and vertical) and now multi-finger gestures. The standard option is 'a two-finger click' for secondary click, though this may not be turned on by default. Visit System Preferences > Trackpad to enable it if it is supported on your machine.
Yes this was a long post, but now you know everything there is to know ;-)
Version 6.0.16_GA_2998.NETWORK Apr 4, 2012 MACOSXx86
Xserve 2x Dual Core Xeons 10GB with Xserve RAID