Ryan Ramage has produced an amazing design tool for JMatter. Here is a snapshot of the designer:
UltraViolet will generate a complete and working JMatter application for you!
IDEA Productivity Templates
I have developed a set of IntelliJ IDEA templates that constitutes a lightweight productivity solution for building JMatter apps. I can no longer write JMatter applications without them.
This tool is documented and can be downloaded from here.
New Project Builder
The upcoming version of JMatter includes a small GUI tool, invoked from Ant, for automatically creating JMatter projects, complete with build file, directory structure, etc..