I know nowdays that their are probably more social networks to join than ever before but i have recently joined a site called Behance.
This is a social network dedicated to creatives around the world, as with most social networks you sign up and then put some of your details in, including choosing a maximum of 5 areas that are your creative disciplines.
Once you’ve done this you also have effectivly build up your portfolio on the site by linking and uploading projects you have done. You can also join ‘circles’ on the site which are essentially like groups dedicated to specific areas of design or specific projects.
I think the site is a great way to meet other creatives and for possible collaboration on projects.