Most popular websites 6 out of 7 powered by GNU/Linux - concludes survey
Pingdom - an uptime monitoring company conducted a survey recently where it researched the technologies that power 7 most popular websites. All these websites except Alexaholic, exclusively use Linux as their choice of OS. Alexaholic is hosted on Windows.
Barring Meebo and Alexaholic, all the rest use Apache web server to serve their web pages. Meebo uses lighttpd - an alternative open source web server and Alexaholic uses IIS.
All the seven websites exclusively use MySQL as their database.