This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Each container has its own implementation of the Servlets API. For example, Tomcat will come with the jar files necessary to compile and run your servlets, and, since it is open source, you can also obtain its source if you like.