Apps on your Mac you may have missed

Go to Finder and select Applications; in addition to any apps that you may have installed, there are many others including:

Dashboard

Go to System Preferences >
Mission control > Show Dashboard

or to display apps press
fn + F12 keys

 

Keyboard Shortcuts

A list of Mac keyboard shortcuts, by no means comprehensive

Buying Second Hand Macs

Thinking of buying second-hand?  Macs are expensive, but generally hold their value better than Windows based computers. You can get an idea of what prices are likely to be on ebay from this website. Bear in mind that these may be higher than than actual sold price.