Besides Facebook and Wikipedia (which I'm not sure why you can exclude them when they are 2 of the top 5 sites on the internet), there is Tumblr and Wordpress.

Besides Facebook and Wikipedia (which I'm not sure why you can exclude them when they are 2 of the top 5 sites on the internet), there is Tumblr and Wordpress. So basically like 90% of the internet. PHP is the choice of the majority of the most "popular" sites in the world. Basecamp, Discourse (really?), and Github get like 1% of the traffic that any of the above sites get.