What IDEs are available on the Mac?

You can find a list of IDEs that work on MacOS 9 here: http://www.outlawcafe.org/developmenttools.html . In general, any IDE written in Java that is compliant with JDK 1.1.x should run on the current version of MRJ.

I'm working on a similar list for MacOS X... however, since MacOS X includes a JDK 1.3 VM, any IDE written in Java should work.