OpenSource

(1) libevent

http://libevent.org/

(2) libev

http://software.schmorp.de/pkg/libev.html

(3) folly - C++11, cloud service, hosted by FB.

https://github.com/facebook/folly

(4) Casablanca - C++11, cloud/web service, hosted by MS

http://msdn.microsoft.com/en-us/devlabs/casablanca

(5) Protobuf - Google

http://code.google.com/p/protobuf/

(6) Apache/Tomcat

(7) Redis

http://redis.io/

(8) memcached

http://memcached.org/

(9) zeromq

http://www.zeromq.org/

(10) Engine X

http://nginx.org/

(11) Hypertable

http://hypertable.org/