Java ME development on Mac OS X
As of this date (June 25, 2008) the only practical solution for Java ME development on Mac OS X seems to be installing Netbeans 6.1 on an alternate operating system (Windows * or Linux) running over VMware Fusion.
Sure, there are a couple of blogs that describe workarounds to getting a Java ME development environment on Mac OS X. JustDev and FaqMobilityMpowerMacOs describe one approach using the MPowerPlayer SDK. Javablog has an article using the MicroEMU WTK.
I tried the former approach with MPowerPlayer and was quite disappointed. The MPowerPlayer emulator crashes quite often even for the simple sample demos that come with NetBeans IDE. Other sample demos that require optional packages such as the Bluetooth demo will not compile. Even open source projects such phoneME that provide these optional packages only cater to Windows (x86) and Linux (x86, ARM).
The latter approach with MicroEMU seemed quite twisted.
Until, Apple updates to JDK 5 Update 14 (version 1.5.0_14) on OS X, I would rather spend $80 on a VMware Fusion license rather than get distracted with little hacks.

There is much more simple solution to use MicroEmulator with Netbeans on the any Java platform: http://plugins.netbeans.org/PluginPortal/faces/PluginDetailPage.jsp?pluginid=10329
@Bartek,
Thanks for the information. I tried the MicroEmulator plugin. The simple demos run fine. But, I have to download additional bits from elsewhere for additional functionality such as JSR 82, JSR 120, etc. and also work without some functionality that is not available at the moment.
I often develop rapid prototypes for a proof of concept. I would not recommend the Microemulator solution to anybody who wants to develop a fully-functional product or a quick demo since the time trade-off is not worth it. At least not as of today