[maxmem]

If you want to watch some of the demos you can check out http://www.demoscene.tv/

[Audiophilip]

Please don't. demoscene.tv is extremely outdated. Youtube is full of excellent quality 60fps video captures of demos. Here's a link to get started: https://www.youtube.com/results?search_query=60fps+demoscene

[NegatioN]

I found that site hard to navigate, and a bit outdated.

For anyone who want a very spesific example of how cool demos can be, here are some of my favorites:

https://www.youtube.com/watch?v=wXMs54NUBOI

https://www.youtube.com/watch?v=xOYpKnl1B_g

https://www.youtube.com/watch?v=OO6dtjxbHzs

Going to see these demo-competitons in Norway in my childhood was certainly a big inspiration to learn coding.