What you could be looking for is a high IQ society or high IQ club. There are people with high IQ all over the world and these groups will allow you to connect with people at your own IQ level. These clubs will require an exam to enter which will assess your IQ level. There is a comprehensive list at http://rationalwiki.org/wiki/High_IQ_society with more information on them.
There is no easy way to know for sure if somebody is smart online without talking to them first but I suggest you start conversations on social networks or discussion forums about topics that interest you and see who comes back with an intelligent response or join an existing conversation that is of interest of you. There is a list of discussions across a lot of forums listed at http://discussionfinder.com/ that could be interesting for you to read.