I used to own a Sega 32x and have been looking for a good emulator for a while. Downloaded Kega the other and have been loving it. It's an all around Sega Emulator: Master System, Genesis, SegaCD, 32x, and GameGear.
I was really surprised when Kega came out for Macs, it is a great emulator, although compatibility with Sega CD is sometimes hit or miss. But still, it's the only Sega CD and 32X emulator for Macs that I know. I still prefer SMS Plus for my Master System/Game Gear duties, but it has largely supplanted Genesis Plus and Generator for me.