Redis - Redis is an open source in-memory data structure project implementing a distributed, in-memory key-value database with optional durability.
Squid Proxy - Website Content Acceleration and Distribution. Thousands of web-sites around the Internet use Squid to drastically increase their content delivery. Squid can reduce your server load and improve delivery speeds to clients.
memcached - High-performance, distributed memory object caching system
CCProxy - Want to share Internet connection? Get every computer online through a single Internet connection?
MongoDB - MongoDB (from "humongous") is a scalable, high-performance NoSQL database.
Apache Traffic Server - Fast, scalable and extensible HTTP/S 2 and 1.1 compliant caching proxy server.