Josh Hoggan from Koingo Software, Inc. just released CrossToolbarKSW, a cool toolbar class where I helped him over the last months with a few issues. Certainly worth taking a look:
If you're waiting for Real Studio to get Cocoa toolbar customization, you may be waiting a while! We've been using this internal solution for a while to manage our toolbars. It is a wrapper class for toolbars in Real Studio that makes use of the MonkeyBread Software plugin set. It focuses on bringing a basic toolbar to Windows, but giving a fully fleshed out toolbar for Mac OS X including customization! Don't be stuck creating two sets of code for a toolbar for each platform any longer. There are a couple features here which don't work (ie. setting the pushed state of a toggle button to False instead of True manually), but they're easily added. Completely open-source and free to use and distribute without restriction.
Grab it here: crosstoolbarksw.zip