Youtube is good because the main video content is right in the middle to scroll through with an easy to access search bar up top and extra tabs such as subscriptions on the left side.
Cookie Clicker has good design as the game seems to divide itself into zones. The big cookie on the left for clicking and visuals, the middle for information about your buildings and the game in general, and the right for buying buildings and upgrades.
Wikipedia articles are set up really cleanly with the main information in the middle and extra information or images about the subject in boxes on the right. It also has the search bar easy to find up top.
6-1: Apply CSS and add color to Koala site