which is the most popular site of making project for engineering student?

Answer 1

Most popular? You don't say what kind of engineering so that leaves answers wide open...

Try searching "engineering student project" in Google. Google's page rank should take care of the rest.

If you want better results, try searching a specific discipline, like "mechanical engineering student project".

Some neat ones not found by those searches:
http://www.makezine.com
http://www.instructables.com (usually simple)