Tomcat in a box
by Volker Weber
This works for Windows, MacOS X and Linux:
For those who are interested in setting up a simple yet effective JSP development environment, or if you just want to learn JSP: A company called Micromata has released a free application entitled Schrödinger. This small 11MB program just needs to be launched, and there you have it, a great little JSP (Java Server Pages) environment.
[via MacOSX Hints]