To a first approximation, there is no Mac software similar to what is available for Windows. S&T,
Street Atlas, and Garmin Mobile PC are considered specialized software -- PNDs are mainstream, laptops are out-of-the-mainstream.
Specialized software tends not to be available for the Mac -- that's the tradeoff that you make when you decide to buy a Mac.
Marvin answered a similar question about
four months ago. I haven't heard of any major changes in the status quo.