What are the best final year projects in computer science and engineering?

Anything with a real world context. If you want to go into industry, then avoid research projects. You need to choose something that uses something that is relevant to a relationship world setting you would be interested in working in, to maximise your chances of finding interest in the job market. Experience almost always wins over knowledge.
The industry or website is almost irrelevant. Choose an area of expertise you want to follow, and if you can choose what you do, build a project around that desire as a real – world example.
But is a web site really your only option? Better to specialise in a specific area and bring something to that area otherwise you will be skilled in the same thing as several million other people. Harder to compete on the job market on something everybody else knows.