In reverse-chronological order:

http://memify.me/ http://leftright.me/ http://mugshotwars.com/ http://brainerdcustody.com/

There are more but these are the apps I've made in the past month or two. I've tried to experiment with a variety of viral techniques and range my projects from local to universal context. The only one that got any notable traffic was Mugshot Wars, but it's tapered off to a few visits a day now.