Nginx, the little Russian web server taking on the giants: "Nginx is a fast, light-weight web server that can also be used as a load balancer and caching server. It’s been written to be able to handle an extremely large number of simultaneous connections in a very efficient manner.
To be able to scale efficiently, nginx does things a bit differently than most web servers. For one, it doesn’t rely on threads to handle requests. Instead it uses a highly scalable asynchronous architecture which makes it possible for it to handle thousands of requests at once without using up a lot of system resources."