At the moment I know of 2 plugins that offer Struts support. NitroX at
http://www.m7.com/ and MyEclipse at http://www.myeclipseide.com/ both
of them are commercial, but I believe both offer trial versions of
their software.

Though if you are just looking for a XML editor, you can try
http://xmlbuddy.com/ It's a lightweight plugin you can use to edit XML
files.

If you want something more sophisticated, there is XDoclet
http://xdoclet.sourceforge.net/xdoclet/index.html that offers automatic
struts-config.xml generation based on comments that you add in the
source files.

Personally  I am picking up XDoclet to generate all the xml
configuration files and edit them if necessary with XMLbuddy.

Just also take a look at www.strutsbox.de. It is a tool that provides a form
based approach to manage your struts-config file.

Daniel