Technical References (online)

Third-party websites
Servlets.com
Jakarta.ee
Eclipse (Genuitec)
Developer.com
Code Geeks
developerWorks
JavaWorld
Oracle Technology Network (OTN)
The ServerSide
Liked Java Libraries - the link

Web ⁄ Application Servers
Jetty and Apache Tomcat versions (6 ⁄ 7 ⁄ 8 ⁄ 9)
Oracle  Glassfish AS 4 ⁄ 6 ⁄ 8 (Payara AS alternative)
IBM WebSphere 5, LittleG (Open Liberty alternative)
BEA Weblogic 5

Operating Systems
GNU Linux Server OS, Mandrake Desktop Linux OS
Microsoft Desktop OS’s