Google+ these days and I encourage you to try it if you haven't, here's why.
If you are using Twitter to build your PLN, search using a hashtag related to education. Cybary Man has a massive list of hashtags used by educators. Search one of those hashtags and see who is using it. Then follow some of the people that are using the hashtag(s) related to your interest(s).
If you are using Google+ to build your PLN, a quick and easy way to find other educators is to go to the Communities section and search for an open community that is centered around a topic that you're interested in. You can simply join the community or you can start to put the individual members into your Google+ circles.