StackOverFriends! lets you log with your Stack account and link your Twitter and Facebook account to look for friends that you have on StackExchange! (your friends have to be on the app, so spread the word and let them know about it!)
I'm developing also the Android app for the app, so stay tuned!
Let me know what you think, if something goes wrong post it here or send me an email. :)
StackOverFriends! is actually closed source because of his development state (it's full of garbage), but I'm thinking about opening it.
I've tested it on Firefox bbut should work on all major browsers.
Build in Java on the server side, Bootstrap for the front-end.