I just started with using LinkedIn (a job network). Would be happy to find international contacts here. If you like, you can add me here:
The people who are already a long time at LinkedIn, how does LinkedIn help you until now?
I am not going to add random people to my Linkedin profile.
Some companies have their own Linkedin profile. Some of them post their vacancies over there.
If you add your classmates to your Linkedin profile you are able to see what kind of internships they had.
You see the names of the companies and if you call those companies you might find a vacancy not published on the firms website.
I also use Linkedin to learn about what kind of projects the companies are doing right now.