Here's a little bit about our development environment...
For operating systems we use Linux and Mac OSX... these work well as each developer system has Java, Tomcat, Sendmail or Postfix, and PostgreSQL loaded.
Developers here are using IntelliJ IDEA and JEdit. We looked into several other solutions but found these two products feature rich and easy to use for both junior and senior developers. NetBeans might be a good alternative as it has just recently been redesigned.
The nice thing about IDEs is that they instantly warn you about coding errors without having to compile first. This alone is a productivity booster.
When we're ready to deploy Centric CRM to Tomcat for testing, we use an Ant script that compiles changed code and copies the files directly to the webapp directory, bypassing the .war generation. The script can be run straight from the IDE if configured to do so and executes in just a few seconds which saves lots of time for those developing Centric CRM vs. creating a complete .war.
This ant script is available with Centric CRM Enterprise, but the same functionality could be adapted in the open source version if needed.
There's much more content in the technical documentation about all the tools we use, so I won't get into too much detail here. Every supporting application we use, from word processing to diagramming is cross-platform (Linux, Mac, Windows).