There are hundreds if not thousands of examples of Scottish Country Dancing on YouTube.
The Box Hill & District Scottish Society suggest the following YouTube examples provide a good introduction to Scottish Country Dancing
Here you will find short videos demonstrating formations such as rights and lefts, hands round and back, grand chain, reels of 3, reels of 4, ladies chain and many more.
This is a well filmed and danced example of a wonderful Scottish dance,the Eightsome Reel
This is an example of a semi professional group of Scottish dancers performing in a dancing competition
This is a group of Russians in beautiful ball gowns dancing a Strathspey
This site has links to YouTube videos of a number of traditional Scottish Country Dances. It is a good place to start if you are looking for a demonstration of a particular dance.
This is a link to a step-by-step guide to some popular dances