The Improve Struts Configuration File Editor for Eclipse includes a graphical view of your Struts actions and JSPs, and includes a struts-config file editor.

If you are using JSPs, you need Struts.

Improves' plug-it makes use of the SolarEclipse plug-in for JSP editing.

Another interesting Eclipse plug-in is CompleteClipse - an enhanced auto-completion widget. Looks interesting.

I'll have a play with both of these at some point.

Oh yes, a couple more interesting ones - XML buddy features syntax highlighting and DTD driven auto-completion, and the Sysdeo Eclipse Tomcat Launcher plug-in, uh, launches Tomcat, but also gives you integrated servlet debugging (with JSP debugging to come), and creates & deploys WAR files.

There are now a huge number of Eclipse plug-ins available - 133 as at the time of writing, according to Eclipse-plugins.2y.net. Looks like Eclipse's promise as a framework for all manner of development tools is starting to come true.