Hazel developer Paul Kim, recently interviewed at Ars Technica’s Infinite Loop, spit out an open-source application to help icon designers test their Mac OS X menu bar icons:
My graphic designer is working on a menu bar icon for the next version of Hazel. To aid my designer in this regard, I threw together a quick little proggie. It’s just a simple program that has a menu bar icon. It provides a controls where you can edit NSStatusItem settings as well as image wells into which you can drag icons. The status item updates so you can see your icons in their natural habitat.