There's a great number of resources available on the web.

• Apache
  • Apache Jserv
  • Jakarta Project
  • Apache
• Servlets
  • Sun's Servlet Website (Java Servlet API)
  • Servlet Central
  • Servlet Forum
• Java
  • Sun: The Source for Java^TM Technology
  • Blackdown.org
    A popular JVM for Linux.
• Books
  • Java Servlet Programming, Jason Hunter (December 1988)
    Though it is starting to become outdated as newer JSDK specifications are released and implemented, this is still a great book for somebody looking to get up to speed on servlets.
  • Java Servlets, Second Edition, Karl Moss (June 1999)
    This book has a lot of great examples.
• JSP
  • Java Server Page Specification
  • GNUJSP
    A free 0.91 implementation of Java Server Pages. The original author of this implementation has stopped his involvement in the development.
  • GnuJsp.home
    However, Paul Siegmann, in true spirit of GNU software, has continued the development at the above link.
  • java.serverpages.com
    Another resource for JSP technology.

1. Java Servlet API Specification 2.1,
   http://java.sun.com/products/servlet/2.1/html/titlepage.fm.html
2. Using Apache Jserv 1.0, Ari Halberstadt
   http://www.servletcentral.com/1999-01/jserv.dchtml